Javascript using reduce function
I have the following array
["0,5,p1", "24,29,p2", "78,83,p2", "78,83,p3", "162,167,p2" ]
I need the output as ["5,p1","10,p2","5,p3"]
, so p1..3 are pay time video files with start and end time. 0.5 p1 medium profile played for 5 seconds, etc. I want to find out how long the total time takes, using an ECMA map script, reduce a function. Here's what I tried but it doesn't work:
var ca = uniqueArray.reduce(function(pval, elem) {
var spl = elem.split(',');
var difference = Math.round(spl[1] - spl[0]);
return difference;
},elem.split(',')[3]);
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4 answers
I don't think it can be done in a single pass, but I could be wrong. I would go 2 steps ...
- Shrink the array to get a unique map of pX values
- Return the result back to an array in the required format
var input = ["0,5,p1", "24,29,p2", "78,83,p2", "78,83,p3", "162,167,p2" ]
var step1 = input.reduce(function(p,c){
var parts = c.split(",");
if(!p[parts[2]])
p[parts[2]] = 0;
p[parts[2]] += parseInt(parts[1],10) - parseInt(parts[0],10);
return p;
},{});
var result = Object.keys(step1).map(function(e){
return step1[e] + "," + e;
});
console.log(result);
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For a one-loop approach, you can use a hash table for the same third parts, eg 'p1'
. If a hash is specified, update the value with the actual delta.
var array = ["0,5,p1", "24,29,p2", "78,83,p2", "78,83,p3", "162,167,p2"],
hash = Object.create(null),
result = array.reduce(function(r, a) {
var parts = a.split(','),
delta = parts[1] - parts[0],
key = parts[2];
if (!(key in hash)) {
hash[key] = r.push([delta, key].join()) - 1;
return r;
}
r[hash[key]] = [+r[hash[key]].split(',')[0] + delta, key].join();
return r;
}, []);
console.log(result);
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I have updated the code. Please check now.
var ca = ["0,5,p1", "24,29,p2", "78,83,p2", "78,83,p3", "162,167,p2" ] .reduce(function(result, elem) {
var spl = elem.split(',');
var difference = Math.round(spl[1] - spl[0]);
var found = false
for (var i = 0 ; i < result.length; i++) {
if (result[i].split(',')[1] == spl[2]) {
result[i] = parseInt(result[i].split(',')[0]) + difference+","+spl[2];
found = true;
}
}
if (!found) result.push(difference+","+spl[2]);
return result;
},[]);
console.log("modified array",ca);
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