分享 17 个常使用高频好用的 JS 代码片段

const defaultSafeValue = "defaultSafeValue"
let someValueNotSureOfItsExistence = null
let expectingSomeValue = someValueNotSureOfItsExistence || defaultSafeValue
console.log(expectingSomeValue)

let someValueNotSureOfItsExistence = null
// let someValueNotSureOfItsExistence = { expectingSomeValue:1 }
let { expectingSomeValue } = someValueNotSureOfItsExistence ||  {}
console.log(expectingSomeValue)

let someValue = true // or some value like 1,.. {} etc
if(someValue){
   console.log('Yes. Its exist')
}

const conditions = ["Condition 2","Condition String2"];someFunction(str){
  if(str.includes("someValue1") || str.includes("someValue2")){
    return true
  }else{
    return false
  }
}

someFunction(str){
   const conditions = ["someValue1","someValue2"];
   return conditions.some(condition=>str.includes(condition));
}

let name = "John Doe", profession = "Engineering"
let someSentence = `My Name is ${name} and he is doing ${profession}`
console.log(someSentence)
// His Name is John Doe and he is doing Engineering

let personObject = {
  name:"John Doe",
  phone:"1234",
  address:{
    line:"abc ave",
    postCode:12223,
  },
}
const {name, phone, address} = personObject;

import { observable, action, runInAction } from 'mobx';

const previousNumber = [1, 3, 5 ];
const allNumbers = [2 ,4 , 6, ...previousNumber];
console.log(allNumbers);
// [ 2, 4, 6, 1, 3, 5 ]
//Handy if you want to merge two objects

var sayHello = (name)=>{
   return "Hello " + name
}
console.log(sayHello("John"))

var sayHello = (name)=> "Hello " + name
console.log(sayHello("John"))

function fn1(){
  console.log('I am Function 1');
}
function fn2(){
  console.log('I am Function 2');
}
let checkValue = 3;
if(checkValue === 3){
 fn1();
}else{
 fn2();
}

(checkValue ===3 ? fn1:fn2)(); // Short Version

var value = true; // or true or some value exist
if(value){
  console.log('Value is there or true')
}
// OR via this way
value && console.log('Value is there or true')

const numberStr1 = "100";
const numberStr2 = "200";
var sampleValue = +numberStr1 + +numberStr2;
console.log(sampleValue);
console.log(typeof sampleValue); // Its a number!

function myFunction(employeeName,jobTitle,yrExp,majorExp){
}
// you can call it via
myFunction("John","Project Manager",12,"Project Management");
//    ***** PROBLEMS ARE *****
// Violation of ‘clean code’ principle
// Parameter sequencing is important
// Unused Params warning if not used 
// Testing need to consider a lot of edge cases.

const mockTechPeople = {
employeeName:'John',
jobTitle:'Project Manager',
yrExp:12,
majorExp:'Project Management'
}

function myFunction({employeeName,jobTitle,yrExp,majorExp}){

     // ES2015/ES6 destructuring syntax is in action
     // map your desired value to variable you need.
}

myFunction(mockTechPeople); // Only One argument

function rectangle(h,w){
 if(!h){
   h=0;
 }else if(!w){
  w=0;
 }
 return h*w;
}
console.log(rectangle())

function rectangle(h =0,w=0){
  return h*w;
}
console.log(rectangle(1,12))

var val = "1212121212"
console.log(Math.floor(val)) // Long one
console.log(~~val) // smart one

var someNumber = 123
console.log(someNumber.toString()) //return "123"
// Or in SHORT CUT
console.log(`${someNumber}`) //return "123"

for(let i=0;i<1e3;i++){ // instead of i<1000, Cool, right?   
}

var x='x',y='y'
var obj = {x,y} // instead of {x:x, y:y}
console.log(obj)

var multiLineString = `some string\n
with multi-line of\n
characters\n`
console.log(multiLineString)