Home > Others

[Redux] Avoiding Array mutations with concat (), slice (), and ... spread

Source: Internet
Author: User
Developer on Alibaba Coud: Build your first app with APIs, SDKs, and tutorials on the Alibaba Cloud. Read more ＞

For Redux, the cannot use mutable methods like Push, splice. Need to use immutable methods such as concat, slice and ... spread

Html:

<!DOCTYPE HTML><HTML><Head>  <MetaCharSet= "Utf-8">  <title>JS Bin</title>  <Scriptsrc= "Https://wzrd.in/standalone/[email protected]"></Script>  <Scriptsrc= "Https://wzrd.in/standalone/[email protected]"></Script></Head><Body></Body></HTML>

Push () vs concat ()

Push:modify the array;

Concat:return a new array;

console.clear (); const AddCounter= (List) = ={List.push (0); returnlist;} Const Testaddcounter= () + ={Const Beforelist= []; Const Afterlist= [0];    Deepfreeze (beforelist); Expect (AddCounter (beforelist)). Toequal (afterlist);} Testaddcounter (); Console.log ("All Tests passing ...");/** "Error" "Typeerror:can" T Add property 0, object was not extensible at AddCounter (Fegewebemu.js:5:8) at TESTADDC Ounter (fegewebemu.js:15:10) at Fegewebemu.js:18:1 "*/console.clear (); const AddCounter= (List) = ={Let res= List.concat (0); returnRes;} Const Testaddcounter= () + ={Const Beforelist= []; Const Afterlist= [0];    Deepfreeze (beforelist); Expect (AddCounter (beforelist)). Toequal (afterlist);} Testaddcounter (); Console.log ("All tests passing.");//passing

Using ... spread:

= (list) +=  {return [... list, 0= () + ={  = [];   = [0];    Deepfreeze (beforelist);    Expect (    addcounter (beforelist)  ). Toequal (afterlist);} Testaddcounter (); Console.log (///  passing

Splice () vs slice ()

Splice:modfiy Array;

Slices:return new Array;

console.clear (); const Removecounter= (list, index) = ={list.splice (index,1); returnlist;} Const Testremovecounter= () + ={Const Beforelist= [0, 10,20]; Const Afterlist= [0, 20];    Deepfreeze (beforelist); Expect (Removecounter (beforelist,1) . toequal (afterlist);} Testremovecounter (); Console.log ("All Tests passing ..."); /** "Error" "Typeerror:cannot Add/remove sealed array elements at Removecounter (Fegewebemu.js:5:8) at Testremoveco Unter (Fegewebemu.js:15:10) at Fegewebemu.js:17:1 "*/console.clear (); const Removecounter= (list, index) = ={  returnList.slice (0, index). Concat (List.slice (Index+1));} Const Testremovecounter= () + ={Const Beforelist= [0, 10,20]; Const Afterlist= [0, 20];    Deepfreeze (beforelist); Expect (Removecounter (beforelist,1) . toequal (afterlist);} Testremovecounter (); Console.log ("All tests passing.");//passing

ES6:

console.clear (); const Removecounter= (list, index) ={    return  [    ...] List.slice (0, index),    + 1)  = () ={  = [0, 10,20];   = [0,];    Deepfreeze (beforelist);    Expect (    1)  ). Toequal (afterlist);} Testremovecounter (); Console.log (///  passing

Modify one element in array:

console.clear (); const Incrementcounter= (list, index) = ={List[index]++; returnlist;}; Const Testincrementcounter= () + ={Const Beforelist= [0, 10,20]; Const Afterlist= [0, 11, 20];    Deepfreeze (beforelist); Expect (Incrementcounter (beforelist,1) . toequal (afterlist);} Testincrementcounter (); Console.log ("All Tests passing ...");/** "Error" "error:expected [0, Ten,] to equal [0, one,] at Object.assert [as default] (Https://wzrd.in/standa Lone/[email protected]:489:9) at expectation.toequal (Https://wzrd.in/standalone/[email protected]:70:26) at TESTINC Rementcounter (fegewebemu.js:16:43) at Fegewebemu.js:18:1 "*/console.clear (); const Incrementcounter= (list, index) = ={Let res= List.slice (0, index). Concat (++List[index]). Concat (List.slice (Index+1)); returnRes;}; Const Testincrementcounter= () + ={Const Beforelist= [0, 10,20]; Const Afterlist= [0, 11, 20];    Deepfreeze (beforelist); Expect (Incrementcounter (beforelist,1) . toequal (afterlist);} Testincrementcounter (); Console.log ("All tests passing.");//passing

ES6:

= (list, index) = {   return  [     ... list.slice (0, index),     + +list [index],     ... list.slice (index+1)   = () = ()=  {= [0, 10,20]  ; = [0, one, one];    Deepfreeze (beforelist);    Expect (    1)  ). Toequal (afterlist);} Testincrementcounter (); Console.log (///  passing

[Redux] avoiding Array mutations with concat (), slice (), and ... spread

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

Related Keywords:
array concat perl array slice learning react functional web development with react and redux php array slice concat array php js array concat concat in javascript array

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

What's Trending
Top 10 Tags
datastax versions naming convention zookeeper client class definition md5 microsoft sql server 2005 data structures exception handling error handling
Top 10 Keywords
microsoft download center down wordpress address url site address url wordpress address url windows installer 4 0 download 302 not found web address url definition site address url wordpress db2 integer mac os installation step by step pdf abbreviation for return

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

Get Started for Free

  • Sales Support

    1 on 1 presale consultation

    Chat Contact Sales

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

    Open a Ticket

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.

    Learn More