不理解，如果有高手看到了，请帮忙解答，谢谢啦~-白红宇

不理解，如果有高手看到了，请帮忙解答，谢谢啦~

阅读量：5297 次

发布时间：2019-06-14

本文共 7448 字，大约阅读时间需要 24 分钟。

例1：

<!DOCTYPE html>

<html>

<head>

<title>菜鸟教程(runoob.com)</title>

</head>

<body>

constructor 属性返回变量或对象的构造函数。

var a=[1,2,3,4];

document.getElementById("demo").innerHTML =

"john".constructor + " " +

(3.14).constructor + " " +

false.constructor + " " +

"b".constructor+" "+

a.constructor + " " +

typeof a.constructor + " " +

a.constructor.toString()+" "+

typeof a.constructor.toString()+" "+

a.constructor.toString().indexOf("Array")+" "+

typeof a.constructor.toString().indexOf("Array")+" "+

//a.constructor.toString().indexOf("Array") > -1+" "+

//typeof a.constructor.toString().indexOf("Array") > -1+" "+

{name:'john', age:34}.constructor + " " +

new Date().constructor + " " +

function () {}.constructor;

</script>

</body>

</html>

例1结果：

constructor 属性返回变量或对象的构造函数。

function String() { [native code] }

function Number() { [native code] }

function Boolean() { [native code] }

function String() { [native code] }

function Array() { [native code] }

function

function Array() { [native code] }

string

number

function Object() { [native code] }

function Date() { [native code] }

function Function() { [native code] }

例2：

<!DOCTYPE html>

<html>

<head>

<title>菜鸟教程(runoob.com)</title>

</head>

<body>

constructor 属性返回变量或对象的构造函数。

var a=[1,2,3,4];

document.getElementById("demo").innerHTML =

"john".constructor + " " +

(3.14).constructor + " " +

false.constructor + " " +

"b".constructor+" "+

a.constructor + " " +

typeof a.constructor + " " +

a.constructor.toString()+" "+

typeof a.constructor.toString()+" "+

a.constructor.toString().indexOf("Array")+" "+

typeof a.constructor.toString().indexOf("Array")+" "+

a.constructor.toString().indexOf("Array") > -1+" "+

//typeof a.constructor.toString().indexOf("Array") > -1+" "+

{name:'john', age:34}.constructor + " " +

new Date().constructor + " " +

function () {}.constructor;

</script>

</body>

</html>

例2 结果：

constructor 属性返回变量或对象的构造函数。

true

例3：

<!DOCTYPE html>

<html>

<head>

<title>菜鸟教程(runoob.com)</title>

</head>

<body>

constructor 属性返回变量或对象的构造函数。

var a=[1,2,3,4];

document.getElementById("demo").innerHTML =

"john".constructor + " " +

(3.14).constructor + " " +

false.constructor + " " +

"b".constructor+" "+

a.constructor + " " +

typeof a.constructor + " " +

a.constructor.toString()+" "+

typeof a.constructor.toString()+" "+

a.constructor.toString().indexOf("Array")+" "+

typeof a.constructor.toString().indexOf("Array")+" "+

a.constructor.toString().indexOf("Array") > -1+" "+

typeof a.constructor.toString().indexOf("Array") > -1+" "+

{name:'john', age:34}.constructor + " " +

new Date().constructor + " " +

function () {}.constructor;

</script>

</body>

</html>

例3结果：

constructor 属性返回变量或对象的构造函数。

false

例4：

<!DOCTYPE html>

<html>

<head>

<title>菜鸟教程(runoob.com)</title>

</head>

<body>

constructor 属性返回变量或对象的构造函数。

var a=[1,2,3,4];

document.getElementById("demo").innerHTML =

"john".constructor + " " +

(3.14).constructor + " " +

false.constructor + " " +

"b".constructor+" "+

a.constructor + " " +

typeof a.constructor + " " +

a.constructor.toString()+" "+

typeof a.constructor.toString()+" "+

a.constructor.toString().indexOf("Array")+" "+

typeof a.constructor.toString().indexOf("Array")+" "+

//a.constructor.toString().indexOf("Array") > -1+" "+

typeof a.constructor.toString().indexOf("Array") > -1+" "+

{name:'john', age:34}.constructor + " " +

new Date().constructor + " " +

function () {}.constructor;

</script>

</body>

</html>

例4结果：

constructor 属性返回变量或对象的构造函数。

true

例5：

<!DOCTYPE html>

<html>

<head>

<title>菜鸟教程(runoob.com)</title>

</head>

<body>

constructor 属性返回变量或对象的构造函数。

var a=[1,2,3,4];

document.getElementById("demo").innerHTML =

"john".constructor + " " +

(3.14).constructor + " " +

false.constructor + " " +

"b".constructor+" "+

a.constructor + " " +

typeof a.constructor + " " +

a.constructor.toString()+" "+

typeof a.constructor.toString()+" "+

a.constructor.toString().indexOf("Array")+" "+

typeof a.constructor.toString().indexOf("Array")+" "+

a.constructor.toString().indexOf("Array") > -1+" "+

{name:'john', age:34}.constructor + " " +

new Date().constructor + " " +

function () {}.constructor+" "+

typeof a.constructor.toString().indexOf("Array") > -1;

</script>

</body>

</html>

例5结果：

constructor 属性返回变量或对象的构造函数。

true

例6：

<!DOCTYPE html>

<html>

<head>

<title>菜鸟教程(runoob.com)</title>

</head>

<body>

constructor 属性返回变量或对象的构造函数。

var a=[1,2,3,4];

document.getElementById("demo").innerHTML =

typeof a.constructor.toString().indexOf("Array") > -1+" "+;

"john".constructor + " " +

(3.14).constructor + " " +

false.constructor + " " +

"b".constructor+" "+

a.constructor + " " +

typeof a.constructor + " " +

a.constructor.toString()+" "+

typeof a.constructor.toString()+" "+

a.constructor.toString().indexOf("Array")+" "+

typeof a.constructor.toString().indexOf("Array")+" "+

a.constructor.toString().indexOf("Array") > -1+" "+

{name:'john', age:34}.constructor + " " +

new Date().constructor + " " +

function () {}.constructor;

</script>

</body>

</html>

例6结果：

constructor 属性返回变量或对象的构造函数。

例7：

<!DOCTYPE html>

<html>

<head>

<title>菜鸟教程(runoob.com)</title>

</head>

<body>

constructor 属性返回变量或对象的构造函数。

var a=[1,2,3,4];

document.getElementById("demo").innerHTML =

typeof a.constructor.toString().indexOf("Array") > -1+" "+

"john".constructor + " " +

(3.14).constructor + " " +

false.constructor + " " +

"b".constructor+" "+

a.constructor + " " +

typeof a.constructor + " " +

a.constructor.toString()+" "+

typeof a.constructor.toString()+" "+

a.constructor.toString().indexOf("Array")+" "+

typeof a.constructor.toString().indexOf("Array")+" "+

a.constructor.toString().indexOf("Array") > -1+" "+

{name:'john', age:34}.constructor + " " +

new Date().constructor + " " +

function () {}.constructor;

</script>

</body>

</html>

例7结果：

constructor 属性返回变量或对象的构造函数。

false

例8：

<!DOCTYPE html>

<html>

<head>

<title>菜鸟教程(runoob.com)</title>

</head>

<body>

constructor 属性返回变量或对象的构造函数。

var a=[1,2,3,4];

document.getElementById("demo").innerHTML =

typeof a.constructor.toString().indexOf("Array") > -1+" "+

"john".constructor + " " +

(3.14).constructor + " " +

false.constructor + " " +

"b".constructor+" "+

a.constructor + " " +

typeof a.constructor + " " +

a.constructor.toString()+" "+

typeof a.constructor.toString()+" "+

a.constructor.toString().indexOf("Array")+" "+

typeof a.constructor.toString().indexOf("Array")+" "+

//a.constructor.toString().indexOf("Array") > -1+" "+

{name:'john', age:34}.constructor + " " +

new Date().constructor + " " +

function () {}.constructor;

</script>

</body>

</html>

例8结果：

constructor 属性返回变量或对象的构造函数。

true

问题：(typeof a.constructor.toString().indexOf("Array")) > -1 的摆放位置决定了最后的结果，该句只有放在最后的时候，输出才是true，其它位置都是false，为什么？

转载于:https://www.cnblogs.com/cyy-13/p/5760260.html

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