How would you merge two optional arrays in Javascript these days? This is the best I got so far:
如何在Javascript中合并两个可选数组？这是我到目前为止最好的：
const trades = this.position.trades; // trades or maintenance can be undefined
const maintenance = this.position.maintenance;
const principals = [... trades ? trades : [], ... maintenance ? maintenance : []];
Looking for elegant solutions while dealing with the fact that either array can be undefined (aka optional). Thanks!
寻找优雅的解决方案，同时处理任何数组都可以未定义的事实（也称为可选）。谢谢！
PS: I'm using Typescript 2.6 / ES6
PS：我正在使用Typescript 2.6 / ES6
2 个解决方案
#1
5
You can do something like this. || this will return [] if the first operand is falsy.
你可以做这样的事情。 ||如果第一个操作数是假的，这将返回[]。
const trades = this.position.trades || [];
const maintenance = this.position.maintenance || [];
const principals = [...trades, ...maintenance];
Or instead of the spread operator just use Array#concat
或者代替扩展运算符只使用Array＃concat
const trades = this.position.trades || [];
const maintenance = this.position.maintenance || [];
const principals = trades.concat(maintenance);
#2
2
You can use the || operator in conjunction with the spread operator which you already use:
你可以使用||运算符与您已使用的扩展运算符一起使用：
const principals = [...this.position.trades || [], ...this.position.maintenance || []];
#1
5
You can do something like this. || this will return [] if the first operand is falsy.
你可以做这样的事情。 ||如果第一个操作数是假的，这将返回[]。
const trades = this.position.trades || [];
const maintenance = this.position.maintenance || [];
const principals = [...trades, ...maintenance];
Or instead of the spread operator just use Array#concat
或者代替扩展运算符只使用Array＃concat
const trades = this.position.trades || [];
const maintenance = this.position.maintenance || [];
const principals = trades.concat(maintenance);
#2
2
You can use the || operator in conjunction with the spread operator which you already use:
你可以使用||运算符与您已使用的扩展运算符一起使用：
const principals = [...this.position.trades || [], ...this.position.maintenance || []];