js的基本课
长度length定义删除尾部
var arr = ['a','b','c'];
arr.length = 2;
console.log(arr[2]); //为 undefined
delete 删除法, 元素占位,长度不变
var arr= ['a','b','c'];
delete arr[0];
console.log(arr); // [undefined,'b','c']
pop()栈 弹出最后一元素并删除之
var arr = ['a','b','c'];
var one = colors.pop();
console.log(one); // "c"
console.log(arr.length); // 2
shift()队列 抽出第一个元素并删除之
var arr = ['a','b','c'];
var one = colors.shift();
console.log(one); // "a"
console.log(arr.length); // 2
foreach查找删除
var arr = ["a", "b", "c"];
arr.forEach(function(item, index, arr) {
if(item === "a") {
arr.splice(index, 1);
}
});
filter过滤删除
var arr = ["a", "b", "c"];
arr = arr.filter(function(item) {
return item != "a"
});
console.log(arr); // ["b", "c"]
splice之删除
//删除起始下标为1,长度为2的一个值(len设置2)
var arr2 = ['a','b','c','d']
arr2.splice(1,2);
console.log(arr2);
//['a','d']
替换
var arr2 = ['a','b','c','d'];
arr2.splice(1,2,'ttt');
console.log(arr2);
//['a','ttt','d'] 替换起始下标为1,长度为2的两个值为‘ttt',len设置的1
插入
var arr = ['a','b','c','d'];
arr.splice(1,0,'ttt');
console.log(arr);
//['a','ttt','b','c','d'] 表示在下标为1处添加一项'ttt'