Javascript Loop with adding same value

Question

I hope you guys can help me!

I'm trying the following:

1000 + 100 = 1100 * 2 = 2200;
2200 + 100 = 2300 * 2 = 4600;
4600 + 100 = 4700 * 2 = 9400;
9400 + 100 = 9500 * 2 = 19000;
...

But I'm getting the flowing result.

1000 + 100 = 1100 * 2 = 2200;
2200 * 2 = 4400
4400 * 2 = 8800
...

The values are inputed by the user, but I used static values for the example.

I have te following code:

var generate = function generate(rate){
    var array = [];
    s=0;
    for (var i = 0; i < 10; i++){
        s =+ 100;
        array.push([
            (parseInt(1000) + 100) * Math.pow(2, i),
        ]); 
    }
    return array;
}

parseInt(1000) is precisely identical to 1000. There's no need for the call to parseInt(). Also, it's +=, not =+. edit oh wait I see, 1000 is a "static value for the example". Fair enough. — Pointy
– Pointy, Commented Mar 3, 2016 at 15:05
Can you describe more clearly what your input, and expected output is? Do you expect an array of numbers or just one number? — Halcyon
– Halcyon, Commented Mar 3, 2016 at 15:05
You're using Math.pow(2, i) but nothing in the sample formulas you posted mention anything about exponents. — Pointy
– Pointy, Commented Mar 3, 2016 at 15:08

Dustin Poissant · Accepted Answer · 2016-03-03 15:10:08Z

1

Sounds to me like you want a function that adds 100, doubles and then calls itself recursively a fixed number of times.

This function will run 10 times and output the final answer:

function add100andDouble(num, runTimes){
  if(runTimes == 0) return num;
  return add100andDouble( (num + 100 ) * 2, runTimes - 1 );
}

$(function(){
  var number = parseFloat(prompt("Enter a number"));
  alert( add100andDouble(number, 10) );
});

answered Mar 3, 2016 at 15:10

Dustin Poissant

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6 Comments

Phylogenesis Over a year ago

This requires jQuery.

Dustin Poissant Over a year ago

What part of this answer requires jQuery?

Phylogenesis Over a year ago

The $(function () { ... }) wrapper.

Dustin Poissant Over a year ago

Ok so then just use window.onload = function(){ ... } is that really so difficult? or put it at the bottom of the body.

Jaromanda X Over a year ago

why would it need to be at the bottom of body, or wrapped in $() ow window.onload? does not rely on DOM readiness at all

|

Vladu Ionut · Accepted Answer · 2016-03-03 15:13:22Z

1

var generate = function generate(rate){
    var array = [];
    s=0;
    for (var i = 0; i < 10; i++){
        s = rate + (array[i-1] ? array[i-1] :1000);
        array.push(s*2); 
    }
    return array;
}
console.log(generate(100));

answered Mar 3, 2016 at 15:13

Vladu Ionut

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Comments

Nina Scholz · Accepted Answer · 2016-03-03 15:17:52Z

1

I suggest to use a function f(x) for calculating the new value. It makes the code more clearly arranged.

function f(x) {
    return (x + 100) * 2;
}

var i = 0,
    x = 1000,
    array = [];

for (i = 0; i < 10; i++) {
    array.push(x);
    x = f(x);
}
document.write('<pre>' + JSON.stringify(array, 0, 4) + '</pre>');

answered Mar 3, 2016 at 15:17

Nina Scholz

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Comments

Raul Ortiz · Accepted Answer · 2016-03-03 15:47:33Z

0

Recursion has its merits on other solutions but I would go with plain old for loop for this situation.

Assuming rate is the starting number, and the return is a fixed 10 value series:

function generate(rate) {
    var series = [];
    for(var i = 0; i < 10; i++) { 
      series.push(rate = ((rate + 100) * 2));
    };
    return series;
}

It can be easily modified to send the series length if needed.

edited Mar 3, 2016 at 15:47

answered Mar 3, 2016 at 15:40

Raul Ortiz

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