Small knowledge, big challenge! This article is participating in the creation activity of “Essential Tips for Programmers”.

Hi everyone, I’m Lonely and I’ve been cleaning up some minor optimizations in code review (sometimes the code is real) ~~

Null, Undefined, Null check

If a variable is null, if a variable is undefined, if a variable is null, if a variable is undefined, if a variable is null, if a variable is null, if a variable is undefined, if a variable is null.

Common writing:

      if(username1 ! = =null|| username1 ! = =undefined|| username1 ! = =' ') {
        let username = username1;
      }
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After the optimization: let the username = with username1 is | | ‘.

(This is also used when assigning default values to variables.)

There are multiple conditions for judging

The way we often use it is:

      if (x === 'png' || x === 'jpeg' || x === 'jpg' || x === 'gif') {
        / / the next step
      }
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A simpler way is to store the values in an array using the includes method:

 if (['png'.'jpeg'.'jpg'.'gif'].includes(x)) {
        / / the next step
      }
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If else optimization

It’s common to see if else nesting

if(val < 0) {}else if(val > 10) {}else( val > 100 ){}Copy the code

If else we can use the ternary operator to optimize if else when the logic inside is small:

let value = val < 0? 'aaa':( val > 10)? 'bbb':'ccc;

The for loop

Common is the common way to write a for loop: for (let I = 0; i < arr.length; i++)

Optimization is written for in or for of: for (let I in arr.length) or for (let I of arr.length)

The switch of the abbreviations

switch (data) {
  case 1:
    test1();
  break;
 
  case 2:
    test2();
  break;
 
  case 3:
    test();
  break;
  
}
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Optimally: Save the condition in a key-value object that can then be used based on the condition.

var data = {
  1: test1,
  2: test2,
  3: test};
data[anything] && data[anything]();
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An object is converted to an array of objects

Object.entries() converts an Object to an array of objects

const data = { a: '111'.b: '222'.c: '333' };
const arr = Object.entries(data);
console.log(arr);
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Shorthand for powers

// Common method
Math.pow(2.3); / / 8


// The shorthand method
2**3 / / 8
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