JavaScript: Return true if an object looks like a Promise, false otherwise
JavaScript fundamental (ES6 Syntax): Exercise-189 with Solution
Write a JavaScript program that returns true if an object looks like a Promise, false otherwise.
- Check if the object is not null, its typeof matches either object or function and if it has a .then property, which is also a function.
Sample Solution:
JavaScript Code:
//#Source https://bit.ly/2neWfJ2
const isPromiseLike = obj =>
obj !== null &&
(typeof obj === 'object' || typeof obj === 'function') &&
typeof obj.then === 'function';
console.log(isPromiseLike({
then: function() {
return '';
}
}));
console.log(isPromiseLike(null));
console.log(isPromiseLike({}));
Sample Output:
true false false
Flowchart:

Live Demo:
See the Pen javascript-basic-exercise-189-1 by w3resource (@w3resource) on CodePen.
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