JavaScript: Get a customized coalesce function that returns the first argument that returns true from the provided argument validation function

JavaScript fundamental (ES6 Syntax): Exercise-42 with Solution

Custom Coalesce Function

Write a JavaScript program to get a customized coalesce function that returns the first argument that returns true from the provided argument validation function.

• Use Array.prototype.find() to return the first argument that returns true from the provided argument validation function, valid.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
// Define a function 'coalesceFactory' that takes a validity check function 'valid' as input and returns another function.
const coalesceFactory = valid => 
  // The returned function takes any number of arguments 'args'.
  (...args) => 
    // Find and return the first argument that passes the validity check.
    args.find(valid);

// Define a custom coalesce function 'customCoalesce' using 'coalesceFactory'.
const customCoalesce = coalesceFactory(_ => ![null, undefined, '', NaN].includes(_));

// Test the 'customCoalesce' function with various arguments and output the result.
console.log(customCoalesce(undefined, null, NaN, '', 'Waldo')); // Output: 'Waldo'

Output:

Waldo

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-1-42 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that returns the first argument for which a given validation function returns true.
• Write a JavaScript function that accepts multiple arguments and a predicate, then returns the first non-null value satisfying the predicate.
• Write a JavaScript program that simulates a coalesce operator by checking each argument with a custom test function.

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