Basis Idea
The basic idea is that we have a function and for some reason we need to make the JS program wait after executing some part of the function
Application
Let's assume that we have a function to find the sum of two numbers and we need to make the program wait 3 second before printing the result
function sumOfTwoNumbers() {
const num1 = 100;
const num2 = 22;
const sum = num1 + num2;
// Wait for 3sec before executing
console.log("The sum is:", sum);
}
Step-1
Create a new function sleep which returns a promise.
This function will make the program wait for the specified milliseconds
Remember 1 second = 1000 millisecond
function sleep(timeInMilliSecond) {
return new Promise((resolve) => setTimeout(resolve, timeInMilliSecond));
}
Step-2
Convert the function (In which we need to make the program wait) to a Asynchronous function
, In our case sumOfTwoNumbers()
// Put keyword async before function keyword to convert function to a asynchronous function
async function sumOfTwoNumbers() {
const num1 = 100;
const num2 = 22;
const sum = num1 + num2;
// Wait for 3sec before executing
console.log("The sum is:", sum);
}
Step-3
Make the program wait for specified amount of milliseconds
async function sumOfTwoNumbers() {
const num1 = 100;
const num2 = 22;
const sum = num1 + num2;
// Add the below line to make the program wait for 3seconds
await sleep(3000);
console.log("The sum is:", sum);
Result
Now the program will wait for 3 seconds before it prints the output
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