JS中typeof、Object.prototype.toString.call、constructor

最新推荐文章于 2024-12-23 12:47:32 发布

原创最新推荐文章于 2024-12-23 12:47:32 发布 · 371 阅读

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本文通过示例代码展示了JavaScript中不同类型变量的检测方法，包括使用typeof、Object.prototype.toString.call及constructor属性进行类型判断。这些方法有助于开发者更好地理解JavaScript的数据类型及其内部实现。

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console.log("-----------typeof o------------");
        console.log("null\t\t\t",       typeof null);
        console.log("{}\t\t\t\t",       typeof {});
        console.log("[]\t\t\t\t",       typeof []);
        console.log("\"a\"\t\t\t\t",    typeof "a");
        console.log("new Date()\t\t",   typeof new Date());
        console.log("1\t\t\t\t",        typeof 1);
        console.log("Number(1)\t\t",    typeof Number(1));
        console.log("undefined\t\t",    typeof undefined);
        console.log("-----------Object.prototype.toString.call(o)------------");
        console.log("null\t\t\t",       Object.prototype.toString.call(null));
        console.log("{}\t\t\t\t",       Object.prototype.toString.call({}));
        console.log("[]\t\t\t\t",       Object.prototype.toString.call([]));
        console.log("\"a\"\t\t\t\t",    Object.prototype.toString.call("a"));
        console.log("new Date()\t\t",   Object.prototype.toString.call(new Date()));
        console.log("1\t\t\t\t",        Object.prototype.toString.call(1));
        console.log("Number(1)\t\t",    Object.prototype.toString.call(Number(1)));
        console.log("undefined\t\t",    Object.prototype.toString.call(undefined));
        console.log("------------o.constructor-----------");
        console.log("{}\t\t\t\t",       {}.constructor);
        console.log("{}\t\t\t\t",       {}.constructor === Object);
        console.log("[]\t\t\t\t",       [].constructor);
        console.log("[]\t\t\t\t",       [].constructor === Array);
        console.log("\"a\"\t\t\t\t",    "a".constructor);
        console.log("\"a\"\t\t\t\t",    "a".constructor === String);
        console.log("new Date()\t\t",   (new Date()).constructor);
        console.log("new Date()\t\t",   (new Date()).constructor === Date);
        console.log("Number(1)\t\t",    Number(1).constructor);
        console.log("Number(1)\t\t",    Number(1).constructor === Number);