[英]HTML Element - Does “value” attribute or property exist?
How can you determine if an html element has a "value" property/attribute? 您如何确定html元素是否具有“值”属性/属性?
Textarea example: Textarea示例:
let textarea = document.createElement("textarea");
textarea.innerHTML = "Sike!";
console.log(textarea.hasAttribute("value")); // returns false (expected true)
console.log(textarea.hasOwnProperty("value")); // returns false (expected true)
console.log(textarea.value); // returns "Sike!";
Div Example: Div示例:
let div = document.createElement("div");
div.innerHTML = "Sike!";
console.log(div.hasAttribute("value")); // returns false (expected false)
console.log(div.hasOwnProperty("value")); // returns false (expected false)
console.log(div.value); // returns undefined; (expected thrown error)
You could test if a property named 'value'
exists in the (non-standard) __proto__
property of your element: 您可以测试元素的(非标准)
__proto__
属性中是否存在名为'value'
属性:
let textarea = document.createElement("textarea"); console.log('value' in textarea.__proto__); console.log('foo' in textarea.__proto__);
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