How JavaScript's Array Reduce Works -

Wes Bos

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Опубликовано:

19 сен 2017

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Комментарии : 24

@rotrose7531 4 года назад

You are genius, thank you. I learnt a lot from this tutorial.

@antonbodnia5788 5 лет назад

another great way const measuredTime = new Date(null); measuredTime.setSeconds(17938); const MHSTime = measuredTime.toISOString().substr(11, 8); "04:58:58"

@abdelrahman5094 4 года назад

what does substr(11,8) do in this code?

@Suneriins234 4 года назад

@@abdelrahman5094 substr(11,8) = Substr(skipallnumbersbeforethisnumber, Outputcharacterslength)).....If you "console.log" this ""const measuredTime = new Date(null); measuredTime.setSeconds(17938); const MHSTime = measuredTime.toISOString()."; you will get this "2020-06-22T10:28:58.918" Because we want to removed "2020-06-22T" and only want to have result in "10:28:58" .Therefore we use "substr(start,lenght)"..substr() will substract all starting numbers and give us result in 8 characters."substr(11.8)..

@MatthewPeck_personal 6 лет назад

How do you have the gutter symbols? Looks like a Git package, or is this Atom?

@limerence-00 6 лет назад

you actually enable my studying)

@anonim1468 6 лет назад

WITH REDUCE const timeNodes = Array.from(document.querySelectorAll('[data-time]')); let seconds = timeNodes.reduce( (total, current, index) => { let [min, sec] = current.dataset.time.split(":").map(parseFloat); return total += min * 60 + sec; }, 0); let hour = seconds / 3600

@lassmadaddeln 5 лет назад

Just a quick note: Since you're not using index i guess you could just omit it.

@elanf 6 лет назад

Hey Wes! What’s your intro song?

@margaritabozhenova8473 4 года назад

Without .map and parseFloat(): const seconds = timeNodes.reduce((total, currValue) => { const [mins, secs] = currValue.dataset.time.split(":"); return total + (mins * 60 + secs * 1); }, 0);

@nathancornwell1455 4 года назад

So, are they automatically coerced into numbers from strings ?

@margaritabozhenova8473 4 года назад

Nathan Cornwell if a String is multiplied by a number, it becomes a number

@nathancornwell1455 4 года назад

Well, i just learned something new . Implicit type coercion .

@uzair004 4 года назад

beautiful one liner :)

@singhkr Год назад

perfect

@snehasamuel7426 Год назад

but why are we doing only floor and not ceil ? Will it be wrong if we do ceil ?

@shiningdragon8737 6 лет назад

How did you get the 3600?

@dominaiter2957 6 лет назад

1 hour = 3600 seconds.

@jean-francoisbouzereau6258 4 года назад

At 5:36. (mins*60)+(secs*1). would have done the trick

@jaimeandrescarcamosepulved2456 Год назад

I wrote a function that takes in seconds' result and returns totalVidTime. Great video! learning a ton with this series. function totalVidTime(seconds){ let hours =Math.floor(seconds/3600); let minutes =Math.floor((seconds/3600%1)*60); let secnd = Math.floor(((seconds/3600%1*60)%1)*60); return `${hours}:${minutes}:${secnd}`; }