[].forEach(function(value, index, array) {// ...
});

var arr = [1,2,3,4];
arr.forEach(function(value,index,array){console.info("index:"+index+" value: "+value);
});

"index:0 value: 1"
"index:1 value: 2"
"index:2 value: 3"
"index:3 value: 4"

$.each([], function(index, value, array) {// ...
});

[].map(function(value,index,array){//code
})

if (!Array.prototype.forEach) {Array.prototype.forEach = function(callback, thisArg) {var T, k; if (this == null) { throw new TypeError("this is null or not defined"); } var O = Object(this); var len = O.length >>> 0; // Hack to convert O.length to a UInt32 if ({}.toString.call(callback) != "[object Function]") { throw new TypeError(callback + " is not a function"); } if (thisArg) { T = thisArg; } k = 0;while (k < len) { var kValue; if (k in O) { kValue = O[k]; callback.call(T, kValue, k, O); } k++; }  };
}

var arr = [];
arr.push(1);
arr.push(2);
arr.push(3);
arr.push(4);
arr.forEach(function(value,index,array){alert("index:"+index+" value: "+value);
});

"index:0 value: 1"
"index:1 value: 2"
"index:2 value: 3"
"index:3 value: 4"

var BreakException = {};
try {[1, 2, 3].forEach(function(v) {console.log(v); //只输出1,2if (v === 2) throw BreakException;});
} catch (e) {if (e !== BreakException) throw e;
}//结果
1
2

[1, 2, 3].forEach(function(v) {if (this.breakFlag === true) {return false;}if (v === 2) {this.breakFlag = true}console.log(v) //只输出1,2
});

var array = [1, 2, 3, 4, 5];
array.forEach(function(item, index) {if (item === 2) {array = array.concat(array.splice(index, array.length - index));}console.log(item); //只输出1,2
});

var a = [1, 2, 3, 4, 5]
a.every(function(item, index, arry) {console.log(item); //返回1,2if (item === 2) {return false} else {return true}
});
var a = [1, 2, 3, 4, 5]
a.some(function(item, index, arry) {console.log(item); //返回1,2if (item === 2) {return true} else {return false}
})

var obj = {a:1, b:2, c:3};
for (var prop in obj) {console.log("obj." + prop + " = " + obj[prop]);
}
// 输出:
// "obj.a = 1"
// "obj.b = 2"
// "obj.c = 3"