javascript 中的 for..in 和 for each..in 有什么区别? [英] What is the difference between for..in and for each..in in javascript?

问题描述

javascript 中的 for..in 和 for each..in 语句有什么区别?是否存在我不知道的细微差别，还是相同且每个浏览器都有不同的名称?

What is the difference between for..in and for each..in statements in javascript? Are there subtle difference that I don't know of or is it the same and every browser has a different name for it?

推荐答案

"for each...in" 在指定对象的所有值上迭代指定变量属性.

"for each...in" iterates a specified variable over all values of the specified object's properties.

示例:

var sum = 0;
var obj = {prop1: 5, prop2: 13, prop3: 8};
for each (var item in obj) {
  sum += item;
}
print(sum); // prints "26", which is 5+13+8

来源

"for...in" 以任意顺序在对象的所有属性上迭代指定变量.

"for...in" iterates a specified variable over all properties of an object, in arbitrary order.

示例:

function show_props(obj, objName) {
   var result = "";
   for (var i in obj) {
      result += objName + "." + i + " = " + obj[i] + "
";
   }
   return result;
}

来源

Note 03.2013，for each... in 循环是已弃用.MDN 推荐的新"语法是 为...的.

Note 03.2013, for each... in loops are deprecated. The 'new' syntax recommended by MDN is for... of.

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