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JavaScript: Build an array, using an iterator function and an initial seed value

JavaScript fundamental (ES6 Syntax): Exercise-111 with Solution

Write a JavaScript program to build  an array, using an iterator function and an initial seed value.

  • Use a while loop and Array.prototype.push() to call the function repeatedly until it returns false.
  • The iterator function accepts one argument (seed) and must always return an array with two elements ([value, nextSeed]) or false to terminate.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const unfold = (fn, seed) => {
  let result = [],
    val = [null, seed];
  while ((val = fn(val[1]))) result.push(val[0]);
  return result;
};
var f = n => (n > 50 ? false : [-n, n + 10]);
console.log(unfold(f, 10));

Sample Output:

[-10,-20,-30,-40,-50]

Flowchart:

flowchart: Build an array, using an iterator function and an initial seed value

Live Demo:

See the Pen javascript-basic-exercise-111-1 by w3resource (@w3resource) on CodePen.


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Next: Write a JavaScript program to unflatten an object with the paths for keys.

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JavaScript: Tips of the Day

Randomizes the order of the values of an array, returning a new array

Example:

const tips_shuffle = ([...arr]) => {
  let x = arr.length;
  while (x) {
    const i = Math.floor(Math.random() * x--);
    [arr[x], arr[i]] = [arr[i], arr[x]];
  }
  return arr;
};
const foo = [2, 4, 6];
console.log(tips_shuffle(foo));

Output:

[4, 2, 6]

 

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