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The JavaScript Interview Handbook: 100+ Interview Questions

Solution Review: Even or Odd?

Explore how to handle asynchronous JavaScript callbacks by learning to create and manage promises that resolve or reject based on whether a number is even or odd. Understand the use of resolve, reject, and setTimeout in promise handling to better grasp asynchronous programming concepts.

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Solution #

Javascript (babel-node)
function evenOdd(num) {
       return new Promise(function(resolve,reject){
        if(isNaN(num)){
            reject("error")
            }
        if((num%2) != 0){
            setTimeout(function(){
                resolve("odd")},1000)
            }
        if(num%2 == 0){
            setTimeout(function(){
                reject("even")},2000)
            }
    });
}
function test(number){
        return evenOdd(number).then(function(result){
            console.log(result)
        }).catch(function(error){
            console.log(error)
        })
}
test(5)
test(1)
test(0)
test(2)
test('abc')

Explanation #

Let’s look at the evenOdd function first. The function takes a number num and returns a new promise. The callback function passed as a parameter to the promise has two parameters: resolve() ...