var arr1 = [1, 2];

var arr2 = arr1;

console.log(arr1); //[1, 2]

console.log(arr2); //[1, 2]

arr1.push(6);

 arr2.push(7);

console.log(arr1); //[1, 2, 6, 7]

console.log(arr2); //[1, 2, 6, 7]

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由以上操作可知简单的 = 赋值都不能达到预想效果，不是新建一个和原对象(数组也是对象)完全一样的对象，而是把原对象的内存地址直接复制给了另一个对象，也就是说两个对象都是指向同一个内存地址

方法一： [].concat()

var arr1 = [1, 2];

var arr2 = [].concat(arr1);

console.log(arr1);//[1, 2]

console.log(arr2);//[1, 2]

arr1.push(6);

arr2.push(7);

console.log(arr1);//[1, 2, 6]

console.log(arr2);//[1, 2, 7]

方法二：JSON.parse(JSON.stringify())

var arr1 = [1, 2];

var arr2 = JSON.parse(JSON.stringify(arr1));

console.log(arr1); //[1, 2]

console.log(arr2); //[1, 2]

arr1.push(6);

arr2.push(7);

console.log(arr1); //[1, 2, 6] 

console.log(arr2); //[1, 2, 7]

方法三：Object.assign({}, arr1);

var arr1 = { a: 0 };

var arr2 = Object.assign({}, arr1);

 console.log(arr1); //{ a: 0 }

console.log(arr2); //{ a: 0 }

arr2.b = 2;

arr1.c = 3;

 arr1.a = 4;

console.log(arr1); //{ a: 4, c: 3}

console.log(arr2); //{ a: 0, b: 2 }

arr2.a = 5;

console.log(arr1); //{ a: 4, c: 3}

console.log(arr2); //{ a: 5, b: 2 }

方法四 直接遍历

var array = [1, 2, 3, 4];

var copyArray = array.slice();

copyArray[0] = 100;

console.log(array); // [1, 2, 3, 4]

console.log(copyArray); // [100, 2, 3, 4]

方法五 slice() 返回一个从已有的数组中截取一部分元素返回新数组（不改变原数组）

var array = [1, 2, 3, 4];

var copyArray = array.slice();

copyArray[0] = 100;

console.log(array); // [1, 2, 3, 4]

console.log(copyArray); // [100, 2, 3, 4]