typescript 两个数组之间的打字稿差异
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Typescript difference between two arrays
提问by Galma88
Is there a way to return the missing values of list_a from list_b in TypeScrpit?
有没有办法从 TypeScrpit 中的 list_b 返回 list_a 的缺失值？
For example:
例如：
var a1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g'];
var a2 = ['a', 'b', 'c', 'd', 'z'];
The result value is
结果值为
['e', 'f', 'g'].
thanks in advance
提前致谢
回答by Nitzan Tomer
There are probably a lot of ways, for example using the Array.prototype.filter():
可能有很多方法，例如使用Array.prototype.filter()：
var a1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g'];
var a2 = ['a', 'b', 'c', 'd'];
let missing = a1.filter(item => a2.indexOf(item) < 0);
console.log(missing); // ["e", "f", "g"]
（操场上的代码）
Edit
编辑
The filterfunction runs over the elements of a1and it reduce it (but in a new array) to elements who are in a1(because we're iterating over it's elements) and are missing in a2.
该filter函数运行在 的元素上a1并将其（但在一个新数组中）减少到a1在a2.
Elements in a2which are missing in a1won't be included in the result array (missing) as the filter function doesn't iterate over the a2elements:
a2缺少的元素a1不会包含在结果数组 ( missing) 中，因为过滤器函数不会遍历a2元素：
var a1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g'];
var a2 = ['a', 'b', 'c', 'd', 'z', 'hey', 'there'];
let missing = a1.filter(item => a2.indexOf(item) < 0);
console.log(missing); // still ["e", "f", "g"]
（操场上的代码）
回答by Ross Scott
Typescript only provides design / compile time help, it doesn't add JavaScript features. So the solution that works in JavaScript will work in Typescript.
Typescript 仅提供设计/编译时帮助，不添加 JavaScript 功能。所以适用于 JavaScript 的解决方案也适用于 Typescript。
Plenty of ways to solve this, my goto choice would be lodash: https://lodash.com/docs#difference
有很多方法可以解决这个问题，我的 goto 选择是 lodash：https://lodash.com/docs#difference
_.difference(['a', 'b', 'c', 'd', 'e', 'f', 'g'],['a', 'b', 'c', 'd']);
