Detailed explanation of destructuring assignment examples for ES6 learning

1. The definition of destructuring assignment

A simple understanding is that the left and right sides of the assignment = sign have the same structure to perform one-to-one assignment statements

2. Classification of destructuring assignment

Array destructuring assignment Object destructuring assignment String destructuring assignment Boolean value destructuring assignment Function parameter destructuring assignment Numerical destructuring assignment ( Just focus on understanding the first two)

3. Explain each category separately

　1. Array Destructuring assignment (the code is shown below, and necessary comments are added for easy understanding)

{
  let a,b,rest;
  [a,b]=[1,2];
  console.log(a,b);//输出1,2 直接将1和2解构到a和b}

　You can also set default values ​​for variables. For example, c in the following code defaults to 3 If deconstruction, for example [a,b,c]=[1,2], c is not deconstructed, then c is undefined

{
  let a,b,c,rest;
  [a,b,c=3]=[1,2];
  console.log(a,b);}

　Usage scenario 1

　　①、Variable exchange　　

{
  let a=1;
  let b=2;
  [a,b]=[b,a];
  console.log(a,b);
}

## Get the result and then retrieve it through the index) 　　

{  function f(){return [1,2]
  }
  let a,b;
  [a,b]=f();
  console.log(a,b);
}

　　③. Only take out some required values ​​​​of the returned result

{  function f(){return [1,2,3,4,5]
  }
  let a,b,c;
  [a,,,b]=f();
  console.log(a,b); // 输出1 4
}

　　④.No Care about the content length of the array

{  function f(){return [1,2,3,4,5]
  }
  let a,b,c;
  [a,...b]=f();
  console.log(a,b);//输出1,[2,3,4,5]
}

{
  let o={p:42,q:true};
  let {p,q}=o;
  console.log(p,q);
}

{
  let {a=10,b=5}={a:3};
  console.log(a,b);//输出3 5
}

{
  let metaData={
    title:'abc',
    test:[{
      title:'test',
      desc:'description'}]
  }
  let {title:esTitle,test:[{title:cnTitle}]}=metaData;
  console.log(esTitle,cnTitle);//abc test （相当于esTitle和cnTitle分别对应metaData里面的abc和test）
}

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