Four methods of JS array splicing [easy to understand]

Hello everyone , I meet you again , I'm your friend, Quan Jun .

var a = [1,2,3,4,5,6];
var b=["foo","bar", "fun"];
 The end result is ：
[1,2,3,4,5,6,"foo","bar","fun"]

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Method 1:concat

c=a.concat(b);

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c It's a new array , At this time, the memory usage is ,c,a,b Three arrays .

Method 2: Do not use new arrays

for(var i=0;i<b.length;i++){ 
   
　　a.push(b[i]);
}
b=null;

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No new array created , Better for memory . Notice the ending b=null; After splicing, the array b Empty .

Method 3:apply( recommend ）

a.push.apply(a,b);

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Method 4:es6 Writing （ recommend ）

a.push(...b);

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