SOURCE

//1.  循环数组，添加元素 
var a = [1,2,3];
var b = [4,5,6];
for(var i in b){
    a.push(b[i]);
}
console.log(a);  //[1,2,3,4,5,6]


//2. 数组连接 concat
var a = [1,2,3];
var b = [4,5,6];
var c = a.concat(b); 
console.log(c); //[1,2,3,4,5,6]


//3. 拼接 splice
var a = [1,2,3,4,5];
a.splice(2,1,6,7); 
console.log(a); //[ 1,2,6,7,4,5]

//3.1 
var a = [1,2,3];
var b = [4,5,6];
a.splice(a.length,0,...b); 
console.log(a);

//4. 直接使用ES6展开运算符
var a = [1,2,3];
var b = [4,5,6];
a = [...a ,...b];
console.log( a); //[1,2,3,4,5,6]