for循环中的变量是一个字符串 [英] Variable in for loop is a string
问题描述
我不确定这是否是正常的行为,但运行这个:
pre $
for(var i in [1, 2,3]){
console.log(i + 1);
$ / code $ / $ p
结果如下:
// 01
// 11
// 21
有人请解释一下,为什么在这种情况下 var i
被视为字符串,而不是如果我为 (var i = 0; i <[1,2,3] .length; i ++)
?
解决方案 i
作为关键字,并且由于对象中的键通常是字符串是的,一个数组是javascript中的一种对象),它将其视为一个String。 I'm not sure if this is normal behavior, but running this: Results in this: Could somebody please explain, why is Its most likely because in this for loop style (for..in), it is treating
这篇关于for循环中的变量是一个字符串的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋! parseInt(i)
在这种情况下工作,但是对于良好的编程习惯,您会想要使用< code $ for循环看起来类似于这样:
$ b $ $ pre $ var $ array $ [1, 2,3];
for(var i = array.length - 1; i> = 0; i--){
//在这里为每个数组元素工作
}
for (var i in [1, 2, 3]) {
console.log(i + 1);
}
// 01
// 11
// 21
var i
being treated like a string in this situation and not if I do for (var i = 0; i < [1, 2, 3].length; i++)
?i
as a key, and since keys in objects are usually strings (yes, an array is a type of object in javascript), it is treating it as a String. parseInt(i)
works in this situation, but for good programming practice, you would want to use a for
loop that looks similar to this:var array = [1, 2, 3];
for (var i = array.length - 1; i >= 0; i--) {
// do work with each array element here
}