本文实例讲述了js实现for循环跳过undefined值的方法。分享给大家供大家参考，具体如下：
<script>
var narr=['a','b','c','d','e'];
console.log(narr);
for (var j=0;j<narr.length;j++){
console.log(j+'=>'+narr[j]);
};
console.log(narr);
for (var j=0;j<narr.length;j++){
console.log(j+'=>'+narr[j]);
if (narr[j] == 'c'){
//narr.splice(j,1);
delete narr[j];
};
};
console.log(narr);
for (var j in narr){
console.log(j+'=>'+narr[j]);
};
/*
(5) ["a", "b", "c", "d", "e"]0: "a"1: "b"3: "d"4: "e"length: 5__proto__: Array(0)
h23.js:4 0=>a
h23.js:4 1=>b
h23.js:4 2=>c
h23.js:4 3=>d
h23.js:4 4=>e
h23.js:7 (5) ["a", "b", "c", "d", "e"]0: "a"1: "b"3: "d"4: "e"length: 5__proto__: Array(0)
h23.js:9 0=>a
h23.js:9 1=>b
h23.js:9 2=>c
h23.js:9 3=>d
h23.js:9 4=>e
h23.js:15 (5) ["a", "b", empty, "d", "e"]0: "a"1: "b"3: "d"4: "e"length: 5__proto__: Array(0)
h23.js:17 0=>a
h23.js:17 1=>b
h23.js:17 3=>d
h23.js:17 4=>e
*/
</script>
运行效果：
这种方式遍历跳过undefined值
PS：这里再为大家推荐一款JS数组遍历方式分析对比工具供大家参考：
在线JS常见遍历方式性能分析比较工具：http://tools.softyun.net/aideddesign/js_bianli
希望本文所述对大家JavaScript程序设计有所帮助。
