How to force Sequential Javascript Execution?

user_226263 0
Viewed 163890

I've only found rather complicated answers involving classes, event handlers and callbacks (which seem to me to be a somewhat sledgehammer approach). I think callbacks may be useful but I cant seem to apply these in the simplest context. See this example:

<html>
  <head>
    <script type="text/javascript">
      function myfunction()  {
        longfunctionfirst();
        shortfunctionsecond();
      }

      function longfunctionfirst() {
        setTimeout('alert("first function finished");',3000);
      }

      function shortfunctionsecond() {
        setTimeout('alert("second function finished");',200);
      }
    </script>
  </head>
  <body>
    <a href="#" onclick="javascript:myfunction();return false;">Call my function</a>
  </body>
</html>

In this, the second function completes before the first function; what is the simplest way (or is there one?) to force the second function to delay execution until the first function is complete?

---Edit---

So that was a rubbish example but thanks to David Hedlund I see with this new example that it is indeed synchronous (along with crashing my browser in the test process!):

<html>
<head>

<script type="text/javascript">
function myfunction() {
    longfunctionfirst();
    shortfunctionsecond();
}

function longfunctionfirst() {
    var j = 10000;
    for (var i=0; i<j; i++) {
        document.body.innerHTML += i;
    }
    alert("first function finished");
}

function shortfunctionsecond() {
    var j = 10;
    for (var i=0; i<j; i++) {
        document.body.innerHTML += i;
    }
    alert("second function finished");
}
</script>

</head>

<body>
  <a href="#" onclick="javascript:myfunction();return false;">Call my function</a>
</body>
</html>

As my ACTUAL issue was with jQuery and IE I will have to post a separate question about that if I can't get anywhere myself!

synchronous execution callback asynchronous javascript
10 Answers

Put your code in a string, iterate, eval, setTimeout and recursion to continue with the remaining lines. No doubt I'll refine this or just throw it out if it doesn't hit the mark. My intention is to use it to simulate really, really basic user testing.

The recursion and setTimeout make it sequential.

Thoughts?

var line_pos = 0;
var string =`
    console.log('123');
    console.log('line pos is '+ line_pos);
SLEEP
    console.log('waited');
    console.log('line pos is '+ line_pos);
SLEEP
SLEEP
    console.log('Did i finish?');
`;

var lines = string.split("\n");
var r = function(line_pos){
    for (i = p; i < lines.length; i++) { 
        if(lines[i] == 'SLEEP'){
            setTimeout(function(){r(line_pos+1)},1500);
            return;
        }
        eval (lines[line_pos]);
    }
    console.log('COMPLETED READING LINES');
    return;
}
console.log('STARTED READING LINES');
r.call(this,line_pos);

OUTPUT

STARTED READING LINES
123
124
1 p is 0
undefined
waited
p is 5
125
Did i finish?
COMPLETED READING LINES
user_51543020
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