JavaScript数组splice方法

var number = [10,3,4,7];

//删除第一位元素 ,0：下标，1：个数
var removed = number.splice(0,1);

console.log(number);//[3, 4, 7]
console.log(removed);//[10]

var number2 = [10,3,4,7];
//插入元素5和8，1：下标1开始，0：删除0个元素，
var removed2 = number2.splice(1,0,5,8)

console.log(number2);//[10, 5, 8, 3, 4, 7]
console.log(removed2);//[]

var number3 = [10,3,4,7];
//替换元素，将3替换为5,8，1：下标1开始，0：删除1个元素。
var removed3 = number3.splice(1,1,5,8)

console.log(number3);//[10, 5, 8, 4, 7]
console.log(removed3);//[]

var arrayIndex = [12,3,4,6,2,1,4];

//从数组开头查询4的下标位置
var indexNum = arrayIndex.indexOf(4);
//从数组末尾查询4的下标位置
var lastIndexNum = arrayIndex.lastIndexOf(4);

var noIndexNum = arrayIndex.indexOf(14);

console.log(indexNum);//2
console.log(lastIndexNum);//6
console.log(noIndexNum);//-1 没有查询到返回-1