synchronous and asynchronous loops in javascript

Question

Are loops synchronous or asynchronous in JavaScript? (for, while, etc)

Supposing I have:

for(let i=0; i<10; i++){
    // A (nested stuff...)
}

//         


        

Answer 1

If you place asynchronous loops inside a for...loop and want to stop the loop until each operation ends, you must use the async/await syntax like this.

async function foo() {
    var array = [/* some data that will be used async*/]

    //This loop will wait for each next() to pass the next iteration
    for (var i = 0; i < array.length; i++) { 
        await new Promise(next=> {
            someAsyncTask(array[i], function(err, data){
                /*.... code here and when you finish...*/
                next()
            })
        })        
    }
}

foo().then(() => { /*After foo execution*/ })