参考

http://*.com/questions/11058384/how-to-delete-specific-array-elements-from-within-a-foreach-loop-in-javascript

https://gist.github.com/chad3814/2924672

for(var f in fruit) {

    if ( fruit[f] == "pear" ) {

        fruit.splice(f, 1);

    }

}

for(var f in fruit) {

    document.write(fruit[f]+"<br>");

}

//

apple

pear

banana

you should handle it in this way

var fruit = ["apple", "pear", "pear", "pear", "banana"],

    i;

for (i = 0; i < fruit.length; ++i) {

    if (fruit[i] === "pear") {

        fruit.splice(i--, 1);

    }

}

console.log(fruit);

//["apple", "banana"]

原理很显然

当我删除第一个pear的时候 数组是apple pear pear banna

此时继续遍历 将从[2]下标开始 有一个pear就会被忽略