reduce

reduce.js

// custom implementation of reduce fn just for fun
Array.prototype.myReduce = function(fn, customStart) {
    var result = customStart ? customStart : null;
    
    for(var i=0;i<this.length;i++) {
        result = fn(result, this[i])
    }
    return result
};
    
// get hash of unique word to frequency
['hi', 'cat', 'bye', 'bye', 'cat', 'h'].reduce(function(prev, curr) {
    prev[curr] = prev[curr] ? prev[curr] += 1 : 1
    return prev
}, {});


// custom Fn should return the same results    
['hi', 'cat', 'bye', 'bye', 'cat', 'h'].myReduce(function(prev, curr) {
    prev[curr] = prev[curr] ? prev[curr] += 1 : 1
    return prev
}, {});