I'm trying to sum values of objects inside and array with underscore.js and its reduce method. But it looks like I'm doing something wrong. Where's my problem?
let list = [{ title: 'one', time: 75 },
{ title: 'two', time: 200 },
{ title: 'three', time: 500 }]
let sum = _.reduce(list, (f, s) => {
console.log(f.time); // this logs 75
f.time + s.time
})
console.log(sum); // Cannot read property 'time' of undefined
Use the native reduce since list is already an array.
reduce callback should return something, and have an initial value.
Try this:
let list = [{ title: 'one', time: 75 },
{ title: 'two', time: 200 },
{ title: 'three', time: 500 }];
let sum = list.reduce((s, f) => {
return s + f.time; // return the sum of the accumulator and the current time, as the the new accumulator
}, 0); // initial value of 0
console.log(sum);Note: That reduce call can be shortened even more if we omit the block and use the implicit return of the arrow function:
let sum = list.reduce((s, f) => s + f.time, 0);
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