{"id":44521,"date":"2023-12-07T16:32:00","date_gmt":"2023-12-07T07:32:00","guid":{"rendered":"https:\/\/kinqsta.com\/jp\/?p=44521&#038;post_type=knowledgebase&#038;preview_id=44521"},"modified":"2025-10-02T04:45:37","modified_gmt":"2025-10-01T19:45:37","slug":"uncaught-typeerror-cannot-set-property","status":"publish","type":"post","link":"https:\/\/kinqsta.com\/jp\/blog\/uncaught-typeerror-cannot-set-property\/","title":{"rendered":"JavaScript\u306e\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u89e3\u6c7a\u65b9\u6cd5"},"content":{"rendered":"<p><a href=\"https:\/\/kinqsta.com\/jp\/blog\/what-is-javascript\/\">JavaScript<\/a>\u3067\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u4f5c\u696d\u3092\u884c\u306a\u3063\u3066\u3044\u308b\u3068\u3001\u8ab0\u3082\u304c\u30a8\u30e9\u30fc\u306b\u906d\u9047\u3059\u308b\u3082\u306e\u3002\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u30a8\u30e9\u30fc\u306b\u3088\u3063\u3066\u306f\u3001\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u304c\u4e00\u6642\u4e2d\u65ad\u3057\u3066\u3057\u307e\u3046\u53ef\u80fd\u6027\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u30a8\u30e9\u30fc\u3092\u52b9\u7387\u7684\u306b\u89e3\u6c7a\u3059\u308b\u306b\u306f\u3001\u30a8\u30e9\u30fc\u30e1\u30c3\u30bb\u30fc\u30b8\u306e\u610f\u5473\u3092\u7406\u89e3\u3057\u306a\u3051\u308c\u3070\u306a\u308a\u307e\u305b\u3093\u3002<\/p>\n<p>\u4eca\u56de\u306fJavaScript\u306e\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u3092\u53d6\u308a\u4e0a\u3052\u307e\u3059\u3002<\/p>\n<p>\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3059\u308b\u3044\u304f\u3064\u304b\u306e\u30b7\u30ca\u30ea\u30aa\u3068\u3001\u305d\u308c\u305e\u308c\u306e\u89e3\u6c7a\u65b9\u6cd5\u3092\u3054\u7d39\u4ecb\u3057\u307e\u3059\u3002\u6700\u5f8c\u306b\u3001\u5909\u6570\u304c<code>null<\/code>\u304b<code>undefined<\/code>\u3067\u3042\u308b\u304b\u3092\u5224\u65ad\u3059\u308b\u65b9\u6cd5\u306b\u3064\u3044\u3066\u3082\u89e6\u308c\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n<div><\/div><kinsta-auto-toc heading=\"Table of Contents\" exclude=\"last\" list-style=\"arrow\" selector=\"h2\" count-number=\"-1\"><\/kinsta-auto-toc>\n<h2>JavaScript\u306e\u300cUncaught TypeError: Cannot Set Property\u300d\u306e\u539f\u56e0<\/h2>\n<p><code>typeerror<\/code>\u306f\u3001\u4e3b\u306b\u4e92\u63db\u6027\u306e\u306a\u3044\u30c7\u30fc\u30bf\u578b\u3092\u542b\u3080\u64cd\u4f5c\u3092\u884c\u3063\u305f\u6642\u306b\u767a\u751f\u3057\u307e\u3059\u3002\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u306e\u5834\u5408\u306f\u3001<code>null<\/code>\u306e\u5024\u3092\u6301\u3064\u30d7\u30ed\u30d1\u30c6\u30a3\u3092DOM\u8981\u7d20\u306b\u5272\u308a\u5f53\u3066\u3088\u3046\u3068\u3057\u3066\u767a\u751f\u3059\u308b<a href=\"https:\/\/kinqsta.com\/jp\/blog\/errors-in-javascript\/\">JavaScript\u30a8\u30e9\u30fc<\/a>\u3067\u3059\u3002<\/p>\n<p>\u3053\u306e\u30a8\u30e9\u30fc\u306f\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u539f\u56e0\u3067\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n<ul>\n<li><code>script<\/code>\u30bf\u30b0\u304c\u30de\u30fc\u30af\u30a2\u30c3\u30d7\u5185\u306e\u8aa4\u3063\u305f\u4f4d\u7f6e\u306b\u914d\u7f6e\u3055\u308c\u3066\u3044\u308b<\/li>\n<li>DOM\u8981\u7d20\u3092\u53c2\u7167\u3059\u308b\u969b\u306e\u5165\u529b\u30df\u30b9<\/li>\n<li>\u672a\u5b9a\u7fa9\u307e\u305f\u306f\u7121\u52b9\u306aDOM\u8981\u7d20\u306b\u30a2\u30af\u30bb\u30b9\u3057\u3088\u3046\u3068\u3057\u3066\u3044\u308b<\/li>\n<\/ul>\n<h2>JavaScript\u306e\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u3092\u89e3\u6c7a\u3059\u308b\u65b9\u6cd5<\/h2>\n<p>\u305d\u308c\u3067\u306f\u3001\u4e0a\u3067\u6319\u3052\u305f3\u3064\u306e\u539f\u56e0\u3092\u6398\u308a\u4e0b\u3052\u3066\u3001\u305d\u308c\u305e\u308c\u306e\u89e3\u6c7a\u65b9\u6cd5\u3092\u3054\u7d39\u4ecb\u3057\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n<p>\u7406\u89e3\u3057\u3084\u3059\u3044\u3088\u3046\u3001\u5b9f\u7528\u7684\u306a\u30b3\u30fc\u30c9\u4f8b\u3092\u7528\u3044\u3066\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n<h3><code>script<\/code>\u30bf\u30b0\u306e\u7121\u52b9\u306a\u914d\u7f6e<\/h3>\n<p>\u30a6\u30a7\u30d6\u30da\u30fc\u30b8\u304c\u8aad\u307f\u8fbc\u307e\u308c\u308b\u969b\u3001\u305d\u306e\u30da\u30fc\u30b8\u306b\u5bfe\u5fdc\u3059\u308bJavaScript\u30b3\u30fc\u30c9\u3082\u540c\u6642\u306b\u8aad\u307f\u8fbc\u307e\u308c\u307e\u3059\u3002JavaScript\u304cDOM\uff08Document Object Model\uff09\u3092\u8a8d\u8b58\u3059\u308b\u65b9\u6cd5\u306f\u3001\u30b3\u30fc\u30c9\u5185\u306e<code>script<\/code>\u30bf\u30b0\u306e\u914d\u7f6e\u306b\u4f9d\u5b58\u3057\u307e\u3059\u3002<\/p>\n<p><code>script<\/code>\u30bf\u30b0\u3092<code>head<\/code>\u30bf\u30b0\u5185\u306b\u7f6e\u3044\u305f\u308a\u3001<code>body<\/code>\u30bf\u30b0\u5185\u306e\u3059\u3079\u3066\u306e<a href=\"https:\/\/kinqsta.com\/jp\/blog\/what-is-html\/\">HTML\u8981\u7d20<\/a>\u306e\u4e0a\u306b\u914d\u7f6e\u3057\u305f\u308a\u3059\u308b\u3068\u3001DOM\u306e\u6e96\u5099\u304c\u3067\u304d\u308b\u524d\u306b\u30b9\u30af\u30ea\u30d7\u30c8\u304c\u5b9f\u884c\u3055\u308c\u307e\u3059\u3002<\/p>\n<p>DOM\u306e\u6e96\u5099\u304c\u3067\u304d\u308b\u524d\u306bJavaScript\u304c\u5b9f\u884c\u3055\u308c\u308b\u3068\u3001DOM\u306e\u5b8c\u5168\u306a\u8868\u73fe\u3092\u53d6\u5f97\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u305b\u3093\u3002\u3064\u307e\u308a\u3001DOM\u8981\u7d20\u306b\u30ea\u30f3\u30af\u3055\u308c\u305f\u5909\u6570\u306e\u307b\u3068\u3093\u3069\u304c<code>null<\/code>\u3068\u3057\u3066\u8fd4\u3055\u308c\u307e\u3059\u3002<\/p>\n<p>\u4ee5\u4e0b\u306f\u3001\u3053\u306e<code>script<\/code>\u30bf\u30b0\u306e\u4f4d\u7f6e\u304c\u539f\u56e0\u3067\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3059\u308b\u30b3\u30fc\u30c9\u4f8b\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-html\">&lt;!DOCTYPE html&gt;\n&lt;html&gt;\n  &lt;head&gt;\n    &lt;title&gt;\u300cUncaught Typeerror\u300d\u30a8\u30e9\u30fc\u306e\u89e3\u6c7a\u65b9\u6cd5&lt;\/title&gt;\n    &lt;script src=\"app.js\"&gt;&lt;\/script&gt;\n  &lt;\/head&gt;\n  &lt;body&gt;\n    &lt;h1 id=\"heading\"&gt;&lt;\/h1&gt;\n  &lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre>\n<p><code>head<\/code>\u30bf\u30b0\u306e\u4e2d\u306b<code>script<\/code>\u30bf\u30b0\u304c\u914d\u7f6e\u3055\u308c\u3066\u304a\u308a\u3001<code>heading<\/code>\u306e<code>id<\/code>\u3092\u6301\u3064<code>h1<\/code>\u8981\u7d20\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u6b21\u306b\u3001<code>h1<\/code>\u8981\u7d20\u306b\u30c6\u30ad\u30b9\u30c8\u3092\u8ffd\u52a0\u3057\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">let heading = document.getElementById('heading');\nheading.textContent = 'This is a heading';\n\/\/Uncaught TypeError: Cannot set properties of null (setting 'textContent')<\/code><\/pre>\n<p>\u4e00\u898b\u554f\u984c\u304c\u306a\u3044\u3088\u3046\u306b\u898b\u3048\u307e\u3059\u304c\u3001\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3057\u307e\u3059\u3002\u3053\u308c\u306f\u3001\u30b9\u30af\u30ea\u30d7\u30c8\u304cDOM\u3088\u308a\u5148\u306b\u8aad\u307f\u8fbc\u307e\u308c\u3001DOM\u8981\u7d20\u304c\u7a7a\u3067\u3042\u3063\u305f\u305f\u3081\u3067\u3059\u3002<\/p>\n<p><code>script<\/code>\u30bf\u30b0\u3092\u4ed6\u306eDOM\u8981\u7d20\u306e\u524d\u306b\u914d\u7f6e\u3057\u305f\u5834\u5408\u306b\u3082\u540c\u3058\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-html\">&lt;!DOCTYPE html&gt;\n&lt;html&gt;\n  &lt;head&gt;\n    &lt;title&gt;\u300cUncaught Typeerror\u300d\u30a8\u30e9\u30fc\u306e\u89e3\u6c7a\u65b9\u6cd5&lt;\/title&gt;\n  &lt;\/head&gt;\n  &lt;body&gt;\n    &lt;script src=\"app.js\"&gt;&lt;\/script&gt;\n    &lt;h1 id=\"heading\"&gt;&lt;\/h1&gt;\n  &lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre>\n<p><code>script<\/code>\u30bf\u30b0\u306f<code>body<\/code>\u30bf\u30b0\u5185\u306eDOM\u8981\u7d20\u306e\u524d\u306b\u7f6e\u304b\u308c\u3066\u3044\u307e\u3059\u304c\u3001\u3053\u306e\u5834\u5408\u3082\u30b9\u30af\u30ea\u30d7\u30c8\u304cDOM\u3088\u308a\u5148\u306b\u8aad\u307f\u8fbc\u307e\u308c\u307e\u3059\u3002<\/p>\n<p>\u3053\u306e\u72b6\u6cc1\u3067\u306e\u89e3\u6c7a\u65b9\u6cd5\u306f\u3001<code>script<\/code>\u30bf\u30b0\u3092<code>body<\/code>\u30bf\u30b0\u3092\u9589\u3058\u308b\u76f4\u524d\u306b\u914d\u7f6e\u3059\u308b\u3053\u3068\u3067\u3059\u3002\u3053\u308c\u306b\u3088\u3063\u3066\u3001\u3059\u3079\u3066\u306eDOM\u8981\u7d20\u304c\u30b9\u30af\u30ea\u30d7\u30c8\u3088\u308a\u5148\u306b\u8aad\u307f\u8fbc\u307e\u308c\u307e\u3059\u3002<\/p>\n<p>\u6b63\u3057\u3044\u914d\u7f6e\u4f8b\u306f\u4ee5\u4e0b\u306e\u3068\u304a\u308a\u3002<\/p>\n<pre><code class=\"language-html\">&lt;!DOCTYPE html&gt;\n&lt;html&gt;\n  &lt;head&gt;\n    &lt;title&gt;Uncaught Typeerror\u30a8\u30e9\u30fc\u306e\u89e3\u6c7a\u65b9\u6cd5&lt;\/title&gt;\n  &lt;\/head&gt;\n  &lt;body&gt;\n    &lt;h1 id=\"heading\"&gt;&lt;\/h1&gt;\n    &lt;script src=\"app.js\"&gt;&lt;\/script&gt;\n  &lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre>\n<pre><code class=\"language-js\">let heading = document.getElementById('heading');\nheading.textContent = 'This is a heading'<\/code><\/pre>\n<p>\u3053\u306e\u30b3\u30fc\u30c9\u3092\u5b9f\u884c\u3059\u308b\u3068\u3001<code>h1<\/code>\u8981\u7d20\u306e<code>textContent<\/code>\u304c\u300cThis is a heading\u300d\u306b\u8a2d\u5b9a\u3055\u308c\u3001\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3059\u308b\u3053\u3068\u306f\u3042\u308a\u307e\u305b\u3093\u3002<\/p>\n<h3>\u5165\u529b\u30df\u30b9<\/h3>\n<p>\u5165\u529b\u30df\u30b9\u3082\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u306e\u539f\u56e0\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p>JavaScript\u3067DOM\u8981\u7d20\u3092\u8b58\u5225\u3059\u308b\u305f\u3081\u306b\u4f7f\u7528\u3059\u308b\u5c5e\u6027\uff08ID\u307e\u305f\u306fclass\uff09\u306e\u5165\u529b\u3092\u8aa4\u308b\u3068\u3001\u5b58\u5728\u3057\u306a\u3044\u8981\u7d20\u3092\u53c2\u7167\u3059\u308b\u3053\u3068\u306b\u306a\u308a\u3001<code>null<\/code>\u304c\u8fd4\u3055\u308c\u307e\u3059 \u3002<\/p>\n<p><code>null<\/code>\u306b\u5024\u3092\u4ee3\u5165\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u3001\u3053\u306e\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n<p>\u30b3\u30fc\u30c9\u4f8b\u3092\u898b\u3066\u307f\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-html\">&lt;!DOCTYPE html&gt;\n&lt;html&gt;\n  &lt;head&gt;\n    &lt;title&gt;\u300cUncaught Typeerror\u300d\u30a8\u30e9\u30fc\u306e\u89e3\u6c7a\u65b9\u6cd5&lt;\/title&gt;\n  &lt;\/head&gt;\n  &lt;body&gt;\n    &lt;h1 id=\"heading\"&gt;&lt;\/h1&gt;\n    &lt;script src=\"app.js\"&gt;&lt;\/script&gt;\n  &lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre>\n<pre><code class=\"language-js\">let heading = document.getElementById('headin');\nheading.textContent = 'Hello World!'\n\/\/Uncaught TypeError: Cannot set properties of null (setting 'textContent')<\/code><\/pre>\n<p>\u3053\u306e\u30b3\u30fc\u30c9\u306e<code>h1<\/code>\u30bf\u30b0\u3067\u306f\u3001<code>id<\/code>\u304c<code>heading<\/code>\u3068\u306a\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>\u307e\u305f\u3001<code>id<\/code>\u3092\u53c2\u7167\u3057\u3066\u3044\u307e\u3059\u304c\u3001\u300cheading\u300d\u304c\u300cheadin\u300d\u306b\u306a\u3063\u3066\u304a\u308a\u3001<code>document.getElementById('heading');<\/code>\u304c\u8aa4\u3063\u3066<code>document.getElementById('headin');<\/code>\u3068\u66f8\u304b\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>\u30a8\u30e9\u30fc\u306e\u767a\u751f\u3092\u907f\u3051\u308b\u305f\u3081\u306b\u306f\u3001\u5e38\u306bDOM\u8981\u7d20\u304c\u6b63\u3057\u304f\u53c2\u7167\u3055\u308c\u3001\u6b63\u3057\u3044\u5c5e\u6027\u3092\u5272\u308a\u5f53\u3066\u3089\u308c\u3066\u3044\u308b\u304b\u3001\u5165\u529b\u30df\u30b9\u304c\u306a\u3044\u304b\u3092\u78ba\u8a8d\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n<h3>\u5b9a\u7fa9\u3055\u308c\u3066\u3044\u306a\u3044DOM\u8981\u7d20\u3078\u306e\u30a2\u30af\u30bb\u30b9<\/h3>\n<p>\u5165\u529b\u30df\u30b9\u540c\u69d8\u3001\u5b58\u5728\u3057\u306a\u3044DOM\u8981\u7d20\u306b\u30a2\u30af\u30bb\u30b9\u3057\u3088\u3046\u3068\u3057\u305f\u5834\u5408\u306b\u3082\u3053\u306e\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n<p>\u4ee5\u4e0b\u306f\u3001\u307e\u3060\u30de\u30fc\u30af\u30a2\u30c3\u30d7\u3067\u5b9a\u7fa9\u3055\u308c\u3066\u3044\u306a\u3044<code>id<\/code>\u5c5e\u6027\u306b\u30a2\u30af\u30bb\u30b9\u3057\u3088\u3046\u3068\u3059\u308b\u4f8b\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-html\">&lt;!DOCTYPE html&gt;\n&lt;html&gt;\n  &lt;head&gt;\n    &lt;title&gt;\u300cUncaught Typeerror\u300d\u30a8\u30e9\u30fc\u306e\u89e3\u6c7a\u65b9\u6cd5&lt;\/title&gt;\n  &lt;\/head&gt;\n  &lt;body&gt;\n    &lt;h1&gt;&lt;\/h1&gt;\n    &lt;script src=\"app.js\"&gt;&lt;\/script&gt;\n  &lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre>\n<pre><code class=\"language-js\">let heading = document.getElementById('headin');\nheading.textContent = 'Hello World!'\n\/\/Uncaught TypeError: Cannot set properties of null (setting 'textContent')<\/code><\/pre>\n<p>\u3053\u306e\u30b3\u30fc\u30c9\u306f\u3001\u5b58\u5728\u3057\u306a\u3044DOM\u8981\u7d20\u306e<code>textContent<\/code>\u3092\u8a2d\u5b9a\u3057\u3088\u3046\u3068\u3057\u3066\u3044\u307e\u3059\u3002HTML\u30b3\u30fc\u30c9\u306b\u306f\u300cheading\u300d\u306e<code>id<\/code>\u3092\u6301\u3064\u8981\u7d20\u306f\u306a\u3044\u305f\u3081\u3001<code>null<\/code>\u304c\u8fd4\u3055\u308c\u307e\u3059\u3002<\/p>\n<p>\u307e\u305f\u3001\u30b3\u30f3\u30bd\u30fc\u30eb\u306b<code>heading<\/code>\u5909\u6570\u306e\u30ed\u30b0\u3092\u51fa\u529b\u3059\u308b\u3068\u3001<code>null<\/code>\u304c\u8fd4\u3055\u308c\u307e\u3059\u3002<\/p>\n<h2>\u5909\u6570\u304cnull\u304bundefined\u3067\u3042\u308b\u304b\u3092\u5224\u65ad\u3059\u308b\u65b9\u6cd5<\/h2>\n<p><code>null<\/code>\u307e\u305f\u306f<code>undefined<\/code>\u306e\u5909\u6570\u306b\u5024\u3092\u4ee3\u5165\u3059\u308b\u3068\u3001\u307b\u3068\u3093\u3069\u306e\u5834\u5408\u306f\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u3092\u89e3\u6c7a\u3067\u304d\u307e\u3059\u3002<\/p>\n<p>\u5909\u6570\u304c<code>null<\/code>\u307e\u305f\u306f<code>undefined<\/code>\u306e\u3069\u3061\u3089\u3067\u3042\u308b\u304b\u3069\u3046\u304b\u306f\u3001\u5909\u6570\u3068\u5bfe\u8a71\u3059\u308b\u524d\u306b\u5224\u65ad\u53ef\u80fd\u3067\u3059\u3002\u3053\u308c\u3067\u30a8\u30e9\u30fc\u304c\u89e3\u6d88\u3067\u304d\u308b\u308f\u3051\u3067\u306f\u3042\u308a\u307e\u305b\u3093\u304c\u3001\u30a8\u30e9\u30fc\u306e\u539f\u56e0\u306f\u660e\u78ba\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p>JavaScript\u3067\u5909\u6570\u304c<code>null<\/code>\u304b<code>undefined<\/code>\u3067\u3042\u308b\u304b\u3092\u5224\u65ad\u3059\u308b\u306b\u306f\u3001<code>null<\/code>\u3068<code>undefined<\/code>\u306e\u5024\u306e\u9055\u3044\u3092\u7406\u89e3\u3059\u308b\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\u3002<\/p>\n<p>\u5909\u6570\u306b\u7a7a\u307e\u305f\u306f\u672a\u77e5\u306e\u5024\u304c\u4ee3\u5165\u3055\u308c\u308b\u3068\u3001\u5909\u6570\u306f<code>null<\/code>\u306b\u306a\u308a\u307e\u3059\uff08<code>null<\/code>\u5909\u6570\u306e\u4f8b\u306f\u4e0a\u3067\u898b\u305f\u3068\u304a\u308a\uff09\u3002<\/p>\n<p>\u5bfe\u3059\u308b<code>undefined<\/code>\u306f\u3001\u5024\u304c\u4ee3\u5165\u3055\u308c\u3066\u3044\u306a\u3044\u5909\u6570\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-js\">let age;\nconsole.log(age);\n\/\/ undefined<\/code><\/pre>\n<p>\u4f8b\u3048\u3070\u3001\u4e0a\u306e\u30b3\u30fc\u30c9\u3067\u306f<code>age<\/code>\u5909\u6570\u304c\u5ba3\u8a00\u3055\u308c\u3066\u3044\u307e\u3059\u304c\u3001\u5024\u306f\u4ee3\u5165\u3055\u308c\u3066\u3044\u307e\u305b\u3093\u3002\u30b3\u30f3\u30bd\u30fc\u30eb\u306b\u30ed\u30b0\u3092\u51fa\u529b\u3059\u308b\u3068\u3001<code>undefined<\/code>\u304c\u8fd4\u3055\u308c\u307e\u3059\u3002<\/p>\n<p><code>null<\/code>\u3068<code>undefined<\/code>\u306e\u9055\u3044\u304c\u308f\u304b\u308c\u3070\u3001\u6b21\u306f\u305d\u306e\u5224\u5225\u65b9\u6cd5\u3067\u3059\u3002<\/p>\n<p>\u3053\u306e2\u3064\u306e\u5909\u6570\u306f\u3001\uff08\u7de9\u3044\uff09\u7b49\u4fa1\u6f14\u7b97\u5b50\uff08<code>==<\/code>\uff09\u3092\u4f7f\u7528\u3057\u3066\u5224\u65ad\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u4f8b\u3092\u898b\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<pre><code class=\"language-html\">&lt;!DOCTYPE html&gt;\n&lt;html&gt;\n  &lt;head&gt;\n    &lt;title&gt;\u300cUncaught Typeerror\u300d\u30a8\u30e9\u30fc\u306e\u89e3\u6c7a\u65b9\u6cd5&lt;\/title&gt;\n  &lt;\/head&gt;\n  &lt;body&gt;\n    &lt;h1 id=\"headin\"&gt;&lt;\/h1&gt;\n    &lt;script src=\"app.js\"&gt;&lt;\/script&gt;\n  &lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre>\n<pre><code class=\"language-js\">let heading = document.getElementById('headin');\nif (heading == null) {\nconsole.log('Variable is null - cannot assign value to a null variable');\n} else {\nheading.textContent = 'Hello World!';\n}<\/code><\/pre>\n<p>\u4e0a\u306e\u30b3\u30fc\u30c9\u306f\u3001DOM\u8981\u7d20\u3092\u53c2\u7167\u3059\u308b\u90e8\u5206\u306b\u5165\u529b\u30df\u30b9\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u307e\u305f\u3001<code>if<\/code>\u6587\u3092\u4f7f\u3063\u3066<code>heading<\/code>\u5909\u6570\u306e\u5024\u304c<code>null<\/code>\u304b\u3069\u3046\u304b\u3092\u30c1\u30a7\u30c3\u30af\u3057\u3066\u3044\u307e\u3059\uff08<code>if (heading == null) {...}<\/code>\uff09\u3002<\/p>\n<p><code>null<\/code>\u3092\u8fd4\u3057\u305f\u305f\u3081\u3001\u30b3\u30f3\u30bd\u30fc\u30eb\u306b\u300cVariable is null &#8211; cannot assign value to a null variable\u300d\u3068\u8868\u8a18\u3055\u308c\u307e\u3059\u3002<code>null<\/code>\u304c\u8fd4\u3055\u308c\u306a\u3044\u3068\u3001<code>else<\/code>\u30d6\u30ed\u30c3\u30af\u306e\u30b3\u30fc\u30c9\u304c\u5b9f\u884c\u3055\u308c\u307e\u3059\u3002<\/p>\n<p><code>if<\/code>\u6587\u306b<code>undefined<\/code>\u3092\u542b\u3081\u306a\u304b\u3063\u305f\u7406\u7531\u306f\u3001JavaScript\u3067\u306f<code>null == undefined<\/code>\u304c\u3067\u3042\u308b\u305f\u3081\u3002<code>if<\/code>\u6587\u3067\u4e21\u65b9\u306e\u30a8\u30e9\u30fc\u3092\u30c1\u30a7\u30c3\u30af\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<h2>\u307e\u3068\u3081<\/h2>\n<p>\u30a8\u30e9\u30fc\u30e1\u30c3\u30bb\u30fc\u30b8\u306f\u6642\u306b\u6df7\u4e71\u3092\u62db\u304d\u307e\u3059\u304c\u3001\u30b3\u30fc\u30c9\u3092\u4fee\u6b63\u3057\u518d\u5ea6\u767a\u751f\u3059\u308b\u3053\u3068\u306e\u306a\u3044\u3088\u3046\u539f\u56e0\u3092\u7a81\u304d\u6b62\u3081\u308b\u624b\u639b\u304b\u308a\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p>\u30a8\u30e9\u30fc\u3092\u597d\u3080\u4eba\u306f\u3044\u307e\u305b\u3093\u304c\u3001<a href=\"https:\/\/kinqsta.com\/blog\/best-programming-language-to-learn\/\">\u666e\u6bb5\u6271\u3046\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u8a00\u8a9e<\/a>\u3092\u3088\u308a\u3088\u304f\u7406\u89e3\u3059\u308b\u6a5f\u4f1a\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n<p>\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u30a8\u30e9\u30fc\u3092\u4fee\u6b63\u3059\u308b\u3053\u3068\u3067\u3001\u5225\u306e\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3067\u4f3c\u305f\u3088\u3046\u306a\u30a8\u30e9\u30fc\u306b\u906d\u9047\u3057\u305f\u969b\u306b\u3001\u3088\u308a\u72b6\u6cc1\u3092\u628a\u63e1\u3057\u3084\u3059\u304f\u306a\u308a\u307e\u3059\u3002\u4eca\u56de\u53d6\u308a\u4e0a\u3052\u305f\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u306f\u3001Vanilla JS\u4ee5\u5916\u3067\u3082\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n<p>\u30a2\u30d7\u30ea\u3084\u30b5\u30a4\u30c8\u3092\u958b\u767a\u3059\u308b\u306b\u306f\u3001<a href=\"https:\/\/kinqsta.com\/blog\/frontend-developer\/\">\u7fd2\u5f97\u3059\u3079\u304d\u30b9\u30ad\u30eb<\/a>\u304c\u3042\u308a\u307e\u3059\u3002\u305d\u3057\u3066\u305d\u306e\u30b9\u30ad\u30eb\u3092\u52b9\u7387\u7684\u306b\u4f7f\u3048\u308b\u3088\u3046\u306b\u306a\u308b\u306b\u306f\u3001<a href=\"https:\/\/kinqsta.com\/jp\/topics\/javascript-tutorials\/\">\u7df4\u7fd2\u306e\u7a4d\u307f\u91cd\u306d<\/a>\u304c\u5fc5\u8981\u3067\u3059\u3002Kinsta\u306e<a href=\"https:\/\/sevalla.com\/pricing\/\">\u30db\u30d3\u30fc\u30d7\u30e9\u30f3<\/a>\u306f\u3001\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u521d\u5fc3\u8005\u304b\u3089\u3001\u81ea\u5206\u306e\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3092\u5ba3\u4f1d\u3057\u305f\u308a\u3001\u6982\u5ff5\u5b9f\u8a3c\u306e\u30a2\u30d7\u30ea\u3092\u30c7\u30d7\u30ed\u30a4\u3057\u305f\u3044\u7d4c\u9a13\u8c4a\u5bcc\u306a\u958b\u767a\u8005\u307e\u3067\u3001\u30c6\u30b9\u30c8\u74b0\u5883\u3092\u5fc5\u8981\u3068\u3059\u308b\u3059\u3079\u3066\u306e\u4eba\u306b\u304a\u52e7\u3081\u3057\u305f\u3044\u30b5\u30fc\u30d0\u30fc\u30d7\u30e9\u30f3\u3067\u3059\u3002\u4eca\u306a\u3089<a href=\"https:\/\/sevalla.com\/pricing\/\">\u521d\u670820\u30c9\u30eb\u5206\u3092\u7121\u6599\u3067<\/a>\u3054\u5229\u7528\u3044\u305f\u3060\u3051\u307e\u3059\u3002<\/p>\n<kinsta-video src=\"https:\/\/www.youtube.com\/watch?v=vmNem6wxfSQ\"><\/kinsta-video>\n","protected":false},"excerpt":{"rendered":"<p>JavaScript\u3067\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u4f5c\u696d\u3092\u884c\u306a\u3063\u3066\u3044\u308b &#8230;<\/p>\n","protected":false},"author":240,"featured_media":44522,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_kinsta_gated_content":false,"_kinsta_gated_content_redirect":"","footnotes":""},"tags":[],"topic":[776],"class_list":["post-44521","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","topic-javascript-errors"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v24.6 (Yoast SEO v24.6) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>JavaScript\u306e\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u89e3\u6c7a\u65b9\u6cd5\uff5cKinsta\u00ae<\/title>\n<meta name=\"description\" content=\"JavaScript\u306e\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u306b\u306f\u3001\u3044\u304f\u3064\u304b\u306e\u539f\u56e0\u304c\u8003\u3048\u3089\u308c\u307e\u3059\u3002\u3053\u306e\u8a18\u4e8b\u3067\u4e3b\u306a\u539f\u56e0\u3068\u89e3\u6c7a\u65b9\u6cd5\u3092\u5b66\u3073\u307e\u3057\u3087\u3046\u3002\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/kinqsta.com\/jp\/blog\/uncaught-typeerror-cannot-set-property\/\" \/>\n<meta property=\"og:locale\" content=\"ja_JP\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"JavaScript\u306e\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u89e3\u6c7a\u65b9\u6cd5\" \/>\n<meta property=\"og:description\" content=\"JavaScript\u306e\u300cUncaught TypeError: Cannot set property\u300d\u30a8\u30e9\u30fc\u306b\u306f\u3001\u3044\u304f\u3064\u304b\u306e\u539f\u56e0\u304c\u8003\u3048\u3089\u308c\u307e\u3059\u3002\u3053\u306e\u8a18\u4e8b\u3067\u4e3b\u306a\u539f\u56e0\u3068\u89e3\u6c7a\u65b9\u6cd5\u3092\u5b66\u3073\u307e\u3057\u3087\u3046\u3002\" \/>\n<meta property=\"og:url\" content=\"https:\/\/kinqsta.com\/jp\/blog\/uncaught-typeerror-cannot-set-property\/\" \/>\n<meta property=\"og:site_name\" content=\"Kinsta\u00ae\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/Kinsta-Japan-334616080691171\/\" \/>\n<meta property=\"article:published_time\" content=\"2023-12-07T07:32:00+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2025-10-01T19:45:37+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/kinqsta.com\/jp\/wp-content\/uploads\/sites\/6\/2023\/04\/uncaught-typeerror-cannot-set-property.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"1460\" \/>\n\t<meta property=\"og:image:height\" 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