zoukankan      html  css  js  c++  java
  • [Ramda] Change Object Properties with Ramda Lenses

    In this lesson we'll learn the basics of using lenses in Ramda and see how they enable you to focus changes on specific properties of an object while keeping your data immutable.

    what 'R.lens' do is able to get or set prop value but keep the object immutable.

    Normally you have 2 ways to use lens:

    1. set up lens: 'lens' + 'prop' + 'assoc';

    After set up you can either get value by using 'R.view';

    Or change a prop by using 'R.set' or 'R.over'.

    2.  Using 'lens' + 'prop' + 'assoc' is a little bit work to do, there is short syntax to do the same thing: 'R.lensProp'.

    const R = require('ramda');
    
    const {view, lens, assoc, prop, set, over, lensProp, toUpper} = R;
    
    const person = {
        firstName: 'Fred',
        lastName: 'Filntstore'
    };
    
    /*
    * What lens does is modify prop value for a given object
    * and keep data immutable.
    * */
    
    const firstNameLens = lens(
        prop('firstName'),
        assoc('firstName')
    );
    const viewFirstName = view(firstNameLens);
    // const result = viewFirstName(person); // Fred
    
    /** Using R.set **/
    const setFirstName = set(firstNameLens);
    const updateFirstName = setFirstName('Zhentian');
    // const result = updateFirstName(person); // { firstName: 'Zhentian', lastName: 'Filntstore' }
    
    /** Using R.over instead of set **/
    const result = over(firstNameLens, toUpper, person);
    
    /** lensProp instead of prop + assoc **/
    const lastNameLens = lensProp('lastName');
    const result2 = over(lastNameLens, toUpper, person); // { firstName: 'Fred', lastName: 'FILNTSTORE' }
    console.log(result);
    console.log(result2);
  • 相关阅读:
    combo,raido
    块级作用域问题ES5 & ES6
    基本类型和引用类型_深拷贝和浅拷贝
    由数组扁平化切入generator函数
    Promise基本用法
    原生ajax请求之前端
    ExtJS组件window
    ORACLE(+) 号的用法,及与逗号运算符的差别
    centos7发布json中文显示乱码
    centos7 svn在repository在的情况下重装恢复
  • 原文地址:https://www.cnblogs.com/Answer1215/p/5947338.html
Copyright © 2011-2022 走看看