JavaScript interview knowledge points and development skills summary

1.bind related usage

Fun.bind (obj) passes obj into the fun as its scope

Fun.bind will return a new function address, fun.bind (obj)!=fun.bind (obj)

Repeated bind only works for the first time

Truth in 2.js

0, "", null, Undefined, false, Nan to Boolean is False

Null = = undefined true

Null = = undefined false

3. Use of expressions

if (a>0)

{

B = True

}

Else

{

B = False

}

should be written as B = a > 0

Complex situations can use local variables or ternary expressions

4. Closures and reference passing

1. All the quotes in the closure are references (simple types are also references!). ）

2.for () var defined in the loop is equivalent to the outside defined var i = 0

Let i = 0 should be used for the for () loop so that I is only visible inside the for loop

3. As a result of this closure, you can see that the loop is complete before returning

var methods = []for (var i = 0; i < ten; i++) {    = (function
   
     () {        console.log ("i ="
     , i)        
    return 
     i    })}methods[0
    ] () VM1405: 5 i = 1010
    = 100100
    methods[0
    ] () VM1405:5 i = 100100
   

The following code exposes a critical error in a for-loop error using closures and VAR declaration iterators

varMethods = [] for(vari = 0; I < 10; i++) {Methods[i]= (function() {Console.log ("I =", i)returni})} methods[0] () VM1196:5 i = 1010 for(vari = 0; I < 10; i++) Methods[i] () VM1196:5 i = 0VM1196:5 i = 1VM1196:5 i = 2VM1196:5 i = 3VM1196:5 i = 4VM1196:5 i = 5VM1196:5 i = 6VM1196:5 i = 7VM1196:5 i = 8VM1196:5 i = 99methods[0] () VM1196:5 i = 1010 for(varj = 0; J < 10; J + +) Methods[j] () 10vm1196:5 i = 10

JavaScript interview knowledge points and development skills summary