for...of与for...in的区别
2016-12-22 14:25
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这两块一直没注意看,现在标一下 。来源MDN
for…of与for…in的区别
for…in循环会遍历一个object所有的可枚举属性。
for…of语法是为各种collection对象专门定制的,并不适用于所有的object.它会以这种方式迭代出任何拥有[Symbol.iterator] 属性的collection对象的每个元素。
下面的例子演示了for…of 循环和 for…in 循环的区别。for…in 遍历每一个属性名称,而 for…of遍历每一个属性值:
for…of与for…in的区别
for…in循环会遍历一个object所有的可枚举属性。
for…of语法是为各种collection对象专门定制的,并不适用于所有的object.它会以这种方式迭代出任何拥有[Symbol.iterator] 属性的collection对象的每个元素。
下面的例子演示了for…of 循环和 for…in 循环的区别。for…in 遍历每一个属性名称,而 for…of遍历每一个属性值:
Object.prototype.objCustom = function () {}; Array.prototype.arrCustom = function () {}; let iterable = [3, 5, 7]; iterable.foo = "hello"; for (let i in iterable) { console.log(i); // logs 0, 1, 2, "foo", "arrCustom", "objCustom" } for (let i of iterable) { console.log(i); // logs 3, 5, 7 }
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