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Filter, Map and Reduce data in JS
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// data format in JSON is just array of objects | |
var data = [{"a":5,"b":24},{"a":11,"b":72},{"a":20,"b":100},{"a":50,"b":257}] | |
// filter object key a > 10 | |
filtered = data.filter(function(datum){ | |
// returning true keeps the object in array | |
if (datum.a > 10) return true | |
}) | |
// map key a to signups and add conversion rate | |
mapped = filtered.map(function(datum, i){ | |
// whatever is returned becomes item in array | |
return { | |
signups: datum.a, | |
conversion: (datum.a / datum.b) * 100 + "%" | |
} | |
}) | |
// reduce all the signups to a total number | |
reduced = mapped.reduce(function (a, b) { | |
// if a is the first item in array | |
if (typeof a === 'object') | |
// b is the next item in array | |
return a.signups + b.signups | |
// a is now the last returned value | |
return a + b.signups | |
}) | |
// Make the data easy on the eyes | |
function prettyJSON(header, data) { | |
var pretty = JSON.stringify(data,null,4) | |
console.log("======" + header + "======>\n\n") | |
console.log(pretty + "\n\n") | |
} | |
// See the data progression | |
prettyJSON("original:", data) | |
prettyJSON("filtered:", filtered) | |
prettyJSON("mapped:", mapped) | |
prettyJSON("reduced:", reduced) | |
// ======original:======> | |
// [ | |
// { | |
// "a": 5, | |
// "b": 24 | |
// }, | |
// { | |
// "a": 11, | |
// "b": 72 | |
// }, | |
// { | |
// "a": 20, | |
// "b": 100 | |
// }, | |
// { | |
// "a": 50, | |
// "b": 257 | |
// } | |
// ] | |
// ======filtered:======> | |
// [ | |
// { | |
// "a": 11, | |
// "b": 72 | |
// }, | |
// { | |
// "a": 20, | |
// "b": 100 | |
// }, | |
// { | |
// "a": 50, | |
// "b": 257 | |
// } | |
// ] | |
// ======mapped:======> | |
// [ | |
// { | |
// "signups": 11, | |
// "conversion": "15.277777777777779%" | |
// }, | |
// { | |
// "signups": 20, | |
// "conversion": "20%" | |
// }, | |
// { | |
// "signups": 50, | |
// "conversion": "19.45525291828794%" | |
// } | |
// ] | |
// ======reduced:======> | |
// 81 | |
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