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JavaScript: Run a given array of promises in series

JavaScript fundamental (ES6 Syntax): Exercise-150 with Solution

Write a JavaScript program to run a given array of promises in series.

  • Use Array.prototype.reduce() to create a promise chain, where each promise returns the next promise when resolved.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const runPromisesInSeries = ps => ps.reduce((p, next) => p.then(next), Promise.resolve());
const delay = d => new Promise(r => setTimeout(r, d));

// Executes each promise sequentially, taking a total of 3 seconds to complete

runPromisesInSeries([() => delay(1000), () => delay(2000)]);

Flowchart:

flowchart: Run an given array of  promises in series

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JavaScript: Tips of the Day

Chunks an array into n smaller arrays

Example:

const tips_chunkIntoN = (arr, n) => {
  const size = Math.ceil(arr.length / n);
  return Array.from({ length: n }, (v, i) =>
    arr.slice(i * size, i * size + size)
  );
}
console.log(tips_chunkIntoN([1, 2, 3, 4, 5, 6, 7,8], 4)); 

Output:

[[1,2],[3,4],[5,6],[7,8]]