MapReduce Utility
Utility that calls one or more map() and reduce() functions over a series of
data.
npm install mattsacks/collect.js
bower install mattsacks/collect.jsOnly the collect() function is exposed.
In node:
var collect = require('collect');In the browser:
<body>
...
<script src="collect.min.js"></script>
</body>collect(data, maps[, options])
The main function, it takes in a dataset and over each item, it runs a map and
reduce function found for each key in maps.
data(Array, Object): A series of data to runmapandreducefunctions on.maps(Object): An object with either a top-levelmapand/orreducefunction defined, or amapand/orreducefunction defined for each key.options(optional Object): a hash of options. Currently unused.
O(n * (number of map and reduce functions defined))
var data = [0, 1, 2];
var maps = {
plusOne: {
map: function(x, i) {
return x + 1;
}
},
sum: {
reduce: function(result, current, x, i) {
return result == null ? current : result + current;
}
}
};
collect(data, maps); // { plusOne: [1, 2, 3], sum: 3 }
maps.plusOneSum = {
map: maps.plusOne.map,
reduce: function(result, current) {
return result + current;
},
init: 0 // initial value for result
};
collect(data, maps); // { plusOne: [1, 2, 3], sum: 3, plusOneSum: 6 }
collect(data, maps.plusOneSum); // 6var data = [0, 1, 2];
// Reference existing maps within
var maps = {
plusOne: {
map: function(x) {
return x + 1;
}
},
sum: {
data: 'plusOne',
reduce: function(result, current) {
return result + current;
},
init: 0
},
times: {
data: 'plusOne',
reduce: function(result, current) {
return result * current;
},
init: 1
}
};
collect(data, maps); // { plusOne: [1, 2, 3], sum: 6, times: 6 };var data = [0, 1, 2];
// Init from the result of another reduce
var maps = {
plusOneSum: {
map: function(x) {
return x + 1;
},
reduce: function(result, current) {
return result + current;
},
init: 0
},
sumPlusOneSum: {
// 6 + 0 + 1 + 2
reduce: function(result, current) {
return result + current;
},
init: 'plusOneSum'
}
};
collect(data, maps); // { plusOneSum: 6, sumPlusOneSum: 9 }var data = [0, 1, 2];
// Reference existing maps within
var maps = {
plusOne: {
map: function(x) {
return x + 1;
}
},
arrays: {
data: 'plusOne',
reduce: function(result, current) {
result.push(this);
return result;
},
init: []
}
};
collect(data, maps);
// {
// plusOne: [1, 2, 3],
// arrays: [[1, 2, 3], [1, 2, 3], [1, 2, 3]]
// }