Sort out some scattered knowledge points by yourself

How to define a function

 // Definition of function declaration 
  function sum(x,y){
    
    return x+y
  }
  console.log(sum(1,2));

  // The form of a function expression 
  let jian = function(x,y){
    
    return x-y
  }
  console.log(jian(5,2));

  // The form of the constructor 
  const sum1 = new Function('x' , 'y' , 'return x + y' )
  console.log(sum1(1,2));

this Point to the problem

var objList = {
    
   name: 'methods',
   getSum: function() {
    
     console.log(this) 
   }
}
objList.getSum()// Point to objlist, Who calls to whom 

function foo() {
    
   console.log(this);
}
foo.apply(undefined);// Point to winodw, If it is null, Is the same 
foo.call(objList);// Point to objlist

call apply bind Method

let obj={
    
    name:" Pan Chenyang ",
    age:18,
    getsum(a,b){
    
        console.log(` My name is ${
      this.name}, This year, ${
      this.age} Years old! ！！！, come from ${
      a}, Go to ${
      b}`);
    }
}
obj.getsum(" nanjing "," anhui ")// My name is panchenyang , This year, 18 Years old! ！！！, From Nanjing , Go to Anhui 

let obj1={
    
    name:" Song Xingyue ",
    age:20
}
obj.getsum.call(obj1," anhui "," nanjing ")// My name is song Xingyue , This year, 20 Years old! ！！！, From Anhui , Go to Nanjing 
obj.getsum.apply(obj1,[" anhui "," nanjing "])// My name is song Xingyue , This year, 20 Years old! ！！！, From Anhui , Go to Nanjing 
obj.getsum.bind(obj1," anhui ",' nanjing ')()// My name is song Xingyue , This year, 20 Years old! ！！！, From Anhui , Go to Nanjing 
obj.getsum.bind(obj1,[" anhui "," nanjing "])()// My name is song Xingyue , This year, 20 Years old! ！！！, From Anhui , nanjing , Go to undefined

What we should pay attention to here is ：call What is passed is a parameter list ,apply What is passed is an array ,bind Not immediately , Instead, it returns a function , Manual call required

Binary system Decimal system transformation

let num = 65
let str = num.toString(2) //10 Binary to binary 
console.log(parseInt(str,2));// Binary conversion 10 Base number