基本的Javascript 2d数组问题

Question

I need to find the intercept between two arrays. Sometime one of them is empty. For this I use underscore.

var fromDB = [[123],[]];
var result = _.intersection(fromDB[0]);

This does not work because fromDB[0] is [123] and not [123],[] . Do you know any way of getting [123],[] ?

Answer 1

You can either specify both of the indexes or use the spread operator .

 var fromDB = [ [123], [] ]; console.log(_.intersection(...fromDB)); console.log(_.intersection(fromDB[0], fromDB[1])); fromDB = [ [123], [123] ] console.log(_.intersection(...fromDB)); console.log(_.intersection(fromDB[0], fromDB[1])); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore.js"></script> 

Answer 2

If you want to access the empty array that you created in fromDB , you need fromDB[1] , that is in this code snippet

_.intersection(fromDB[0],fromDB[1]);

I guess this is what you wanted .