Wherever interview, you will not avoid es6, then as a program ape, decided to study under es6, their learning ability is poor, very slow to learn something, to learn for a long time, just a little clue, the line did not talk much , quickly put up notes on!
1. The first is the wording of the definition of variables, can be repeated until a var statement, let ---- now have block-level variable definition can not be repeated statement that is defined within the function, then it can only be used within the function, not the global, then it is less than, this benefit is to prevent data pollution; const definitions for fixed, such as domain name, address or something;
2. arrow function - this I began to think good trouble, so hard, but learned later found that lecturers would say the same is the function of shorthand,
Previous wording
let a=function(){}
Arrow function
let a=()=>{return a}
If there is only one parameter {}, {} may be omitted
let a=()=>return a;
Correcting this, relatively normal point
3. function parameters
Is a general pattern of function a (a, b, c, d)
You can now write function (a, b, ... args) ------ (... args) represents the remaining parameters but only as a last argument can be extended to collect
let data=[12,5,8,9];
let arr = [... data, .. data]; Extended
4. deconstruction assignment
Such as defining a variable let a = 10, b = 2;
You can write to let [a, b] = [10,2], what type of left and right correspond to the type of assignment
5. array
Array es6 more than four methods ---
map, mapping a one of [1,6,5,4] can be mapped to [in January, June, May, April];
let result = Array.map (item => Data)
For example let data = [20,60,80,50] ----- data.map (? Item => item> 60 'pass': 'fail');
reduce, summary
let data=[20,60,80,50]；
Results item-- tmp-- calculated value, index-- array index
data.reduce((tmp,item,index)=>{
if(index!data.length-1){
return tmp + item; plus a first value and a second value, and processing is continued if the value of the third .......
}else{
}
})
filter, leaving a portion of the filter puncturing part ----
let data=[20,60,80,50]；
// returns the data is divisible by 3 of true; data.filter (item => item% 3 == 0)
forEach, loop (iteration)
let data=[20,60,80,50]；
data.forEach((item,index)=>{
Operation data portion
})
6. string
More than two new methods startsWith endsWith;
let data="sadhkjashdkj";
data.startWith ( 's') // first string is determined not begin with s
data.endsWith ( 'j') // first string is determined not to end j
------------- can be used to determine mail and web site
String template
Previous string concatenation is then str = '', str + = '.........'
You can now be written as: str = `` If you have content you want to insert the variable value with $ {variable name} can be inserted
7.JSON
JSON object
let json = {a: 12, b: 5}; --- json wording
JSON.stringify (json) ---- becomes a string
let json="{"a":12,"b":23}"
Standard wording - only with all the names must have double quotes double quotes wrap, or will be error
JSON.parse(json)---变成json
JSON shorthand
json name with the value (key and value) the same as when you can just write a let json = {a: a} =========== let json = {a}
8.promise
We are generally asynchronous data synchronization request
Asynchronous: multiple requests at the same time, the code becomes complicated;
Synchronization: You can only do one thing, the code is simple;
Both strengths and weaknesses, so there is a promise to eliminate asynchronous, synchronous operation code of the method
General wording:
resolve-- success reject-- failure
let p=new Promise(function(resolve,reject){
For example, request here
$.ajax({
url:'.........',
dataType:'json',
success(data)=>{
resolve(data)
},error(error)=>{
reject(error)
}
})
})
Call words: p.then (function () {}, --- the successful function function () {} --- failure function)
If multiple requests at the same time, it may be used Promise.all ([Request 1, Request 2]). Then ()
You may encapsulate promise
GreatePromist function // (URL) {
// return new new Promise (function (Resolve, Reject) {
// $ .ajax (URL, {
// dataType: 'json', // server returns json data format
// type: ' post ', // HTTP request type
// timeout: 10000, // timeout is set to 10 seconds;
// success: function (Data) {
// Resolve (Data); // successful return
//},
// error : function (error) {
// Reject (error); // else return
//}
//});
//})
//}
Then call is Promise.all ([Request 1, Request 2]). Then ()
In fact, jquery package itself has promise in version 3. More than
So we can Promise.all ([$ ajax ({url1, dataType: 'json'}), $ ajax ({url2, dataType: 'json'}),..]) Then ();.
9.generator generator
Request for logic, do half the things you can pause
Detailed https://www.liaoxuefeng.com/wiki/1022910821149312/1023024381818112
To es7 when this method can be used instead of async await specific can first look at Baidu