web reptile explanation -URLLIB Library Ruddy -Basic use -timeout settings -automatic simulation HTTP request

2023-01-23   ES  

recently used the arrow function in the project frequently, in the process of usingreturnKeyword usage is more confused. The following methods are recorded:

  • If the code block of the arrow function is more than one sentence, you need to use large brackets to include them and usereturnKeyword Return

Example:

const foo = (a, b) => {
    
   a+b;
}
foo(1, 2) // undefined

const foo1 = (a, b) => {
    
   return a+b;
}
foo1(1, 2) // 3

All the parts that are included in brackets If you want to get the return value, you must use itreturnKeywords return, otherwise returnundefined

  • If the arrow function only has a line of sentences, it can omit large brackets and omitreturnKeywords.
    Example:
const foo = (a, b) => a+b // equivalent to const foo = (a, b) => {return a+b}
foo(1, 2) // 3

Herefoo = (a, b) => a+bequivalent tofoo = (a, b) => { return a+b }

The above usage can be used to simplify the callback function, see the following example:

// Normal function writing
[1,2,3].map(function (x) {
    
  return x * x;
});

// Arrow function writing
[1,2,3].map(x => x * x);

can be seen, we used the arrow function to omit the function{}returnKeywords make the function more concise.

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