映射对象数组并按javascript中的键分组

Question

How can I succinctly achieve the following manipulation in javascript:

[ {key:'a', value:1}, {key:'a', value:2}, {key:'b', value:4} ]

->

{'a':[1,2], 'b':[4] }

Code simplicity is what I'm really going for and I am already using lodash but I couldn't really figure out how to do this manipulation.

Answer 1

Try using reduce :

 var arr = [ {key:'a', value:1}, {key:'a', value:2}, {key:'b', value:4} ]; var obj = arr.reduce(function(acc, x) { if (!acc[x.key]) acc[x.key] = []; acc[x.key].push(x.value); return acc; }, {}); document.write(JSON.stringify(obj)); 

See MDN docs on reduce for more information.

If you have to support IE8 or below (which doesn't have reduce ), you could use a polyfill , or you could manually loop over the array and set object keys as you go (which would look uglier). It looks like lodash also already has a reduce function, too .