The Problem
Javascript offers a number of different ways to iterate over an array. Recently while using the array.forEach syntax, I came across some interesting behaviour when using them with the async/await syntax.
To demonstrate. Lets take the following Javascript code which simply prints some messages to the console every 2 seconds.
function waitForTwoSecs(i) {
return new Promise(resolve => {
setTimeout(() => {
console.log(`loop iteration ${i}`);
resolve('resolved');
}, 2000);
});
}
async function mainProgram() {
const loopIterations = [1, 2, 3];
console.log('mainProgram Start');
loopIterations.forEach(async iteration => {
const result = await waitForTwoSecs(iteration);
});
console.log('mainProgram finished');
}
mainProgram();