javascript calculate x of a number

Question

I am wondering how in javascript if i was given a number  say 10000  and then was given a percentage  say 35 8    how would I work out how much that is  eg 3580

User · Answer

If you want to pass the   as part of your function you should use the following alternative    lt script gt  function fpercentStr quantity  percentString        var percent   new Number percentString replace                return fpercent quantity  percent      function fpercent quantity  percent        return quantity   percent   100    document write  test 1       fpercent 10000  35 873   document write  test 2       fpercentStr 10000   35 873      lt  script gt

User · Answer

Your percentage divided by 100  to get the percentage between 0 and 1  times by the number  35 8 100 10000

User · Answer

var result    35 8   100    10000     Thank you jball for this change of order of operations  I didn t consider it

User · Answer

var number   10000  var result    358   number

User · Answer

Best thing is to memorize balance equation in natural way   Amount   Whole   Percentage   100     usually You have one variable missing  in this case it is Amount  Amount   10000   35 8   100   then you have high school math  proportion  to multiple outer from both sides and inner from both sides   Amount   100   358 000  Amount   3580   It works the same in all languages and on paper  JavaScript is no exception

User · Answer

I use two very useful JS functions  http   blog bassta bg 2013 05 rangetopercent-and-percenttorange   function rangeToPercent number  min  max      return   number - min     max - min        and  function percentToRange percent  min  max       return  max - min    percent   min

User · Answer

It may be a bit pedantic   redundant with its numeric casting  but here s a safe function to calculate percentage of a given number   function getPerc num  percent        return Number num  -   Number percent    100    Number num          Usage  getPerc 10000  25

User · Answer

This is what I would do      num is your number    amount is your percentage function per num  amount     return num amount 100          lt html goes here gt       alert per 10000  35 8

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Harder Way  learning purpose     var number   150 var percent  10 var result   0 for  var index   0  index  lt  number  index         const calculate   index   number   100    if  calculate    percent  result    index   return result

User · Answer

In order to fully avoid floating point issues  the amount whose percent is being calculated and the percent itself need to be converted to integers   Here s how I resolved this   function calculatePercent amount  percent        const amountDecimals   getNumberOfDecimals amount       const percentDecimals   getNumberOfDecimals percent       const amountAsInteger   Math round amount    e  amountDecimals         const percentAsInteger   Math round percent    e  percentDecimals         const precisionCorrection    e-  amountDecimals   percentDecimals   2          add 2 to scale by an additional 100 since the percentage supplied is 100x the actual multiple  e g  35 8  is passed as 35 8  but as a proper multiple is 0 358       return Number  amountAsInteger   percentAsInteger    precisionCorrection      function getNumberOfDecimals number        const decimals   parseFloat number  toString   split      1        if  decimals            return decimals length             return 0     calculatePercent 20 05  10      2 005   As you can see  I    Count the number of decimals in both the amount and the percent Convert both amount and percent to integers using exponential notation Calculate the exponential notation needed to determine the proper end value Calculate the end value   The usage of exponential notation was inspired by Jack Moore s blog post   I m sure my syntax could be shorter  but I wanted to be as explicit as possible in my usage of variable names and explaining each step

[javascript] javascript: calculate x% of a number

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