为什么此增量不起作用？

Question

I'm having some problems with this code. My problem is that with the code below, it doesn't plus the detection-ratio text with the 'incr'. It just enters the incr, but doesn't plus.

---

This is my code.

(function loop() {
    var rand = Math.round(Math.random() * (3000 - 500)) + 500;
    var incr=Math.floor(Math.random()*6);
    setTimeout(function() {
         document.getElementById('detection-ratio').innerText = '0 / '+ ++incr;
         loop();  
    }, rand);
}());

---

The 'detection-ratio' text looks like this as default:

0 / 0

Then, lets say 'incr' generates the number '3', then it should increase the last 0 with 3, so it would look like this:

0 / 3

Then, lets say it's going to generate a new 'incr', lets say '5'. Then it would look like this:

0 / 8

---> But right now, it doesn't do that. It just writes the 'incr' into the 'detection-ratio' without increasing it.

Answer 1

I am assuming you are trying to append text to detection-ratio if so you need to

document.getElementById('detection-ratio').innerText += '0 / '+ incr;

++ before a variable is a pre-increment operator, since you are generating random numbers i am assuming that is not actually what you want.

Answer 2

Hope this code would help you to get the expected output, let me know if something breaks. Also stop iteration once it reaches > 26

var incr = 0;   
    (function loop() {
            var rand = Math.round(Math.random() * (3000 - 500)) + 500;
            incr +=  Math.floor(Math.random()*6);
            setTimeout(function() {
                 console.log('0 / '+ incr);
                 loop();  
            }, rand);
    }());

Thanks for the explanation and patience.

Answer 3

Since you're calling the loop recursively anyway, you may want to consider a more functional approach:

(function loop(startctr) {
        var rand = Math.round(Math.random() * (3000 - 500)) + 500;
        nextctr = startctr + Math.floor(Math.random()*6);
        setTimeout(function() {
             console.log('0 / '+ nextctr);
             loop(nextctr);  
        }, rand);
}(0));