CODEWITHSUNDEEP
javascriptpromise
Usman
Usman

Reputation: 87

JavaScript promises beginner

I have been trying to learn promises recently, but I am hitting a roadblock? any suggestions: Can you tell me, what I am doing wrong here?

function printstring(string) {
  return new promise( function (resolve,reject) {
    setTimeout(function () {
      document.write(string);
      resolve();
    }, Math.floor(Math.random() * 100) + 1;)
  })
}

function printall() {
  printstring("A")
    .then(function () { return printString("C"); })
}

printall();

Upvotes: 0

Views: 94

Answers (4)

Matus Dubrava
Matus Dubrava

Reputation: 14462

You have a lot of typos in your code.

  • promise should be Promise with capital P
  • printString("C") should be printstring("C")
  • Math.floor(Math.random() * 100) + 1;) should be Math.floor(Math.random() * 100) + 1);

If you want to observe how setInterval together with Promise works in this case then increase its delay (although it works just fine with any value).

function printstring(string) {
  return new Promise( function (resolve,reject) {
    setTimeout(function () {
      document.write(string);
      resolve();
    }, Math.floor(Math.random() * 1000) + 1);
  })
}

function printall(){
  printstring("A")
    .then(function () { return printstring("C"); })
}
printall();

Just a small note, avoid using document.write(string);, it is really an old style way of placing content to your website. Instead use something like innerHTML or textContent. In this particular case, you could replace that line with document.body.textContent += string;.

Upvotes: 2

guru
guru

Reputation: 282

    function printstring(string) {
        return new Promise( (resolve, reject)=> {
            setTimeout(
                () => {
                    console.log(string);
                    resolve();
                }, Math.floor(Math.random() * 100) + 1);

        })
    }

    function printall() {

        printstring("A")
            .then(function () {
                return printstring("C");
            })

    }
    printall();




    Better use Es6 arrow functions.this makes your code cleaner.
  i was using node so replaced document.write with console.log

Upvotes: 1

Beginner
Beginner

Reputation: 9095

function printString(string){
    return new Promise(function(resolve, reject){
        setTimeout(function(){
            document.write(string);
            resolve();
        }, Math.floor(Math.round() * 100) +1)
    })
}

function printAll(){
    printString("Test").then(function(res){
        printString("<br>sample<br>");
    })
}

printAll();

promise should be Promise (Start with Capital P) see doc Promise in JavaScript

Upvotes: 0

cgolding
cgolding

Reputation: 116

When creating an instance of Promise, you're doing it in lower case, should be new Promise not new promise.

Upvotes: 0

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