Make writing a habit together! This is the fourth day of my participation in the “Gold Digging Day New Plan · April More text Challenge”. Click here for more details.

As we all know, JS has a lot of tricks (tricks), although some basic use is rarely, but accidentally encountered, at least to be able to read it ~

Don’t say more words, directly open blunt ~

Trick 1: Two sets of logic and or

Look at the following code snippet:

let a="one",b="two",c="three";

let d = a && b && c; 

console.log(d)
Copy the code

Output what?

Is that true? Or one of one/two/three?

The correct answer is:

// "three"
Copy the code

To:

let a = "",b="two",c="three";

let d = a && b && c; 

console.log(d)
Copy the code

Output what?

Is false? Or one of /two/three?

The answer is:

/ / ""Copy the code

Wait, before you jump to conclusions, let’s look at the “or” operation:

let a="one",b="two",c="three";

let d = a || b || c; 

console.log(d)
Copy the code

Is the output still three?

False, the result is:

 // "one"
Copy the code

Then look at:

let a = "",b="two",c="three"; 

let d = a || b || c;

console.log(d)
Copy the code

The output is:

  // "two"
Copy the code

Oh oh ~ see here, must have a big smart guess the truth ~~

  • AND (&&)

Two sets of logical and (&&) operators represent:

When each of these values is “true”, the last value is taken;

When there is a value of “false”, the first value is “false”;

  • OR (||)

Two groups of logic or (| |) operator said:

When there is a value “true”, the first value is “true”;

When each of these values is false, the last value is taken;

Trick 2: Sets the variable to key

Sometimes you encounter the requirement that the key of an object is a variable; So how do we set that up?

Like this?

var stu_address = 'address';
var student = {
    name:'mick',
    age : 10,
    stu_address : 'chennai'    
    
}
// {name:'mick', age : 10, stu_address : 'chennai'}
Copy the code

Output, did not achieve the desired effect.

“Trick” came on!

var stu_address = 'address';
var student = {
    name:'mick',
    age : 10,
    [stu_address] : 'chennai'    
    
}

//{name: 'mick', age: 10, address: 'chennai'}
Copy the code

If the key in the object is wrapped with [], the key can be set as a dynamic key.

Trick 3: Data and object conversion

This is common, but important and useful

Array to object:

Let arr =,2,3,4,5,6,7,8,9 [1] const convert_obj = {... arr}; / / {" 0 ": 1," 1 ": 2," 2 ": 3," 3 ": 4," 4 ", 5, "5" : 6, "6", 7, "7" : 8, "8" : 9, "9" : 10}Copy the code

Object to array:

let obj = {
            one : 'a',
            two : 'b',
            three : 'c'
        };

/*1. Object.keys*/

         const keys = Object.keys(obj) //['one', 'two', 'three']

/*2. Object.values*/             
           
           const values = Object.values(obj) // ['a', 'b', 'c']

/*3. Object.entries*/

             const entries = Object.entries(obj) // [ ["one", "a"], ["two", "b"], ["three","c"] ]
Copy the code

For this melon, the first trick is still good drop, usually used less, can strengthen understanding;

OK, the above is the share, hope can help ~

Think good, give a three link 👍👍👍

I’m Nuggets Anthony, output exposure input, technical insight into life.