jquery array group by

Question

I have array like this

abcArr = [[\"A\", 10], [\"B\", 20], [\"A\",30],[\"C\",40]]

how can I group and sum values by A, B, C...

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Answer 1

Underscore.js has groupBy, and the rest can be done by mapping over reduce (that is, reducing each group to one element

abcArr = [["A", 10], ["B", 20], ["A",30],["C",40]]

var grouped = _.groupBy(abcArr, function(x){return x[0]})
var result  = _.map(grouped, function(x){
    return _.reduce(x, function(x,y){
        return [y[0], x[1]+y[1]];
    }, [,0])
})

http://jsfiddle.net/srvKQ/

Or (minified)

abcArr = [["A", 10], ["B", 20], ["A",30],["C",40]]

var result = _.map(
    _.groupBy(abcArr, function(x){return x[0]}),
    function(x){return _.reduce(
        x, function(x,y){return [y[0], x[1]+y[1]]}, [,0]
)});

http://jsfiddle.net/srvKQ/1/