JavaScript使用类似break机制中断forEach循环的方法

javascript数组对象，有一个foreach方法，可枚举每一个数组元素，但并不支持类似for循环的break语法，中断循环：

[1,2,3].foreach(function(item) {
  // if(!item) break; 不支持
});

解决办法，可抛出一个特殊异常，来中断foreach循环，原理：

var breakexception = {};
try {
[1, 2, 3].foreach(function(el) {
console.log(el);
if (el === 2) throw breakexception;
});
} catch (e) {
if (e !== breakexception) throw e;
}

也可复写foreach方法：

// use a closure to prevent the global namespace from be polluted.
(function() {
// define stopiteration as part of the global scope if it
// isn't already defined.
if(typeof stopiteration == "undefined") {
stopiteration = new error("stopiteration");
}
// the original version of array.prototype.foreach.
var oldforeach = array.prototype.foreach;
// if foreach actually exists, define foreach so you can
// break out of it by throwing stopiteration. allow
// other errors will be thrown as normal.
if(oldforeach) {
array.prototype.foreach = function() {
try {
oldforeach.apply(this, [].slice.call(arguments, 0));
}
catch(e) {
if(e !== stopiteration) {
throw e;
}
}
};
}
})();

使用

// show the contents until you get to "2".
[0,1,2,3,4].foreach(function(val) {
if(val == 2)
throw stopiteration;
alert(val);
});

总结

以上所述是小编给大家介绍的javascript使用类似break机制中断foreach循环的方法，希望对大家有所帮助