不太理解这个for循环和变量声明位置对返回值的影响

Question

function findLongestWord(str) {  var arr = [];  arr = str.split(" ");  str = arr[0];  for(var i = 0; i < arr.length; i++) {     if(arr[i].length > str.length) {      str = arr[i];    }  }  return str.length;}findLongestWord("The quick brown fox jumped over the lazy dog");  //6function findLongestWord(str) {  var arr = [];  arr = str.split(" ");  for(var i = 0; i < arr.length; i++) {     str = arr[0];    if(arr[i].length > str.length) {      str = arr[i];    }  }  return str.length;}findLongestWord("The quick brown fox jumped over the lazy dog");  //3为什么是3？

Answer 1

function findLongestWord(str) {

    var arr = [];

    arr = str.split(' ');

    for (var i = 0,str = arr[0]; i < arr.length; i++) {

        if (arr[i].length > str.length) {

            str = arr[i];

        }

    }

    return str.length;

}

var result = findLongestWord('The quick brown fox jumped over the lazy dog');

console.log(result);

for的每次循环开始都会执行一遍str = arr[0];，结果自然不对啦~把这个赋值放到var i = 0的后边（都是初始化赋值嘛）就可以了。