What s the most elegant way to cap a number to a segment

Question

Let s say x  a and b are numbers  I need to limit x to the bounds of the segment  a  b   In other words  I need a clamp function  clamp x    max  a  min x  b     Can anybody come up with a more readable version of this

User · Answer

Update for ECMAScript 2017   Math clamp x  lower  upper    But note that as of today  it s a Stage 1 proposal  Until it gets widely supported  you can use a polyfill

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My favorite    min x max  sort   1

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A simple way would be to use Math max min  Math min number  max     and you can obviously define a function that wraps this  function clamp number  min  max      return Math max min  Math min number  max        Originally this answer also added the function above to the global Math object  but that s a relic from a bygone era so it has been removed  thanks  Aurelio for the suggestion

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In the spirit of arrow sexiness  you could create a micro clamp constrain gate  amp c  function using rest parameters  var clamp       v    gt  v sort  a b    gt  a-b  1     Then just pass in three values  clamp 100 -3 someVar     That is  again  if by sexy  you mean  short

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This expands the ternary option into if else which minified is equivalent to the ternary option but doesn t sacrifice readability  const clamp    value  min  max    gt      if  value  lt  min  return min    if  value  gt  max  return max    return value     Minifies to 35b  or 43b if using function   const clamp  c a l   gt c lt a a c gt l l c   Also  depending on what perf tooling or browser you use you get various outcomes of whether the Math based implementation or ternary based implementation is faster  In the case of roughly the same performance  I would opt for readability

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If you are able to use es6 arrow functions  you could also use a partial application approach   const clamp    min  max    gt   value    gt      value  lt  min   min   value  gt  max   max   value   clamp 2  9  8      8 clamp 2  9  1      2 clamp 2  9  10      9  or  const clamp2to9   clamp 2  9   clamp2to9 8      8 clamp2to9 1      2 clamp2to9 10      9

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If you don   t want to define any function  writing it like Math min Math max x  a   b  isn   t that bad

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This does not want to be a  quot just-use-a-library quot  answer but just in case you re using Lodash you can use  clamp    clamp yourInput  lowerBound  upperBound    So that    clamp 22  -10  10        gt  10  Here is its implementation  taken from Lodash source         The base implementation of    clamp  which doesn t coerce arguments         private     param  number  number The number to clamp      param  number   lower  The lower bound      param  number  upper The upper bound      returns  number  Returns the clamped number      function baseClamp number  lower  upper      if  number     number        if  upper     undefined          number   number  lt   upper   number   upper            if  lower     undefined          number   number  gt   lower   number   lower              return number     Also  it s worth noting that Lodash makes single methods available as standalone modules  so in case you need only this method  you can install it without the rest of the library  npm i --save lodash clamp

User · Answer

The way you do it is pretty standard  You can define a utility clamp function           Returns a number whose value is limited to the given range        Example  limit the output of this computation to between 0 and 255     x   255  clamp 0  255         param  Number  min The lower boundary of the output range     param  Number  max The upper boundary of the output range     returns A number in the range  min  max      type Number     Number prototype clamp   function min  max      return Math min Math max this  min   max         Although extending language built-ins is generally frowned upon

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a less  Math  oriented approach  but should also work   this way  the  lt      test is exposed  maybe more understandable than minimaxing  but it really depends on what you mean by  readable   function clamp num  min  max      return num  lt   min   min   num  gt   max   max   num

[javascript] What's the most elegant way to cap a number to a segment?

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