1.类型分析: js中的数据类型有undefined,boolean,number,string,object等5种,前4种为原始类型,第5种为引用类型. 代码 var a1; var a2 = true; var a3 = 1; var a4 = "Hello"; var a5 = new Object(); var a6 = null; var a7 = NaN; var a8 = undefined; alert(typeof a); //显示"undefined&
Sometime you need to check one prop exists on the object and value should not be ´null´ or ´undefined´. One problem people may occur with: const {get} = require('lodash') } const existing = typeof get(obj, 'a') !== undefined // true Here we missed if
In this lesson, we’ll use a Maybe to safely operate on properties of an object that could be undefined. We’ll use our initial code as the basis for a prop utility function that can be reused with different objects and various property names. Instead