关于push和concat的性能问题

var arr1 = [1,2,3,-1]
var arr2 = [4,5,6,7,8,9,10,12,13,14,15,16,17,18,29,30,31,32,33,34,35,36,37,38,39,40]
var arr  = arr1.concat(arr2)


借用apply方法 ，push、splice也可和来连接数组。因为push没有创建新数组，如果想要保挂原对象的引用，可使用push方法。

var testConcat = function(abc) {
  var arr1 = [1,2,3,-1]
  var arr2 = [4,5,6,7,8,9,10,12,13,14,15,16,17,18,29,30,31,32,33,34,35,36,37,38,39,40]
  var arr  = arr1.concat(arr2)
}

var testPush = function(abc) {
  var arr1 = [1,2,3,-1]
  var arr2 = [4,5,6,7,8,9,10,12,13,14,15,16,17,18,29,30,31,32,33,34,35,36,37,38,39,40]
  Array.prototype.push.apply(arr1, arr2)
}

var count = 1000000

var date = Date.now()
for (var i = 0; i < count; i++) {
    testConcat()
}
console.log(Date.now() - date)

var date = Date.now()
for (var i = 0; i < count; i++) {
    testPush()
}

console.log(Date.now() - date) 

结果：

时间：

1470

465

json什么时候用数组，如果频繁添加删除的尽量用json，因为这是数组的短处，如果频繁取数据的用数组。