Switch statement for greater-than less-than

Question

so I want to use a switch statement like this   switch  scrollLeft      case   lt 1000        do stuff    break    case   gt 1000  amp  amp   lt 2000        do stuff    break      Now I know that either of those statements   lt 1000  or   gt 1000  amp  amp   lt 2000  won t work  for different reasons  obviously    What I m asking is the most efficient way to do just that   I hate using 30 if statements  so I d rather use the switch syntax   Is there anything that I can do

User · Answer

I hate using 30 if statements

I had the same situation lately, that's how I solved it:

before:

if(wind_speed >= 18) {
    scale = 5;
} else if(wind_speed >= 12) {
    scale = 4;
} else if(wind_speed >= 9) {
    scale = 3;
} else if(wind_speed >= 6) {
    scale = 2;
} else if(wind_speed >= 4) {
    scale = 1;
}

after:

var scales = [[4, 1], [6, 2], [9, 3], [12, 4], [18, 5]];
scales.forEach(function(el){if(wind_speed > el[0]) scale = el[1]});

And if you set "1, 2, 3, 4, 5" then it can be even simpler:

var scales = [4, 6, 9, 12, 18];
scales.forEach(function(el){if(wind_speed >= el) scale++});

User · Answer

In my case  color-coding a percentage  nothing performance-critical   I quickly wrote this   function findColor progress        const thresholds    30  60       const colors      90B451     F9A92F     90B451         return colors find  col  index    gt            return index  gt   thresholds length    progress  lt  thresholds index

User · Answer

What exactly are you doing in   do stuff   You may be able to do something like    scrollLeft  lt  1000      do stuff    scrollLeft  gt  1000  amp  amp  scrollLeft  lt  2000      do stuff    scrollLeft  gt  2000      do stuff     etc

User · Answer

switch  Math floor scrollLeft 1000       case 0       lt 1000       do stuff    break    case 1       gt  1000  amp  amp   lt 2000       do stuff     break      Only works if you have regular steps     EDIT  since this solution keeps getting upvotes  I must advice that mofolo s solution is a way better

User · Answer

You can create a custom object with the criteria and the function corresponding to the criteria  var rules      lowerLimit  0     upperLimit  1000  action  function1                    lowerLimit  1000  upperLimit  2000  action  function2                    lowerLimit  2000  upperLimit  3000  action  function3       Define functions for what you want to do in these cases  define function1  function2 etc   And  evaluate  the rules  function applyRules scrollLeft       for var i 0  i gt rules length  i                var oneRule   rules i          if scrollLeft  gt  oneRule lowerLimit  amp  amp  scrollLeft  lt  oneRule upperLimit                     oneRule action                      Note     I hate using 30 if statements   Many times if statements are easier to read and maintain  I would recommend the above only when you have a lot of conditions and a possibility of lot of growth in the future    Update As  Brad pointed out in the comments  if the conditions are mutually exclusive  only one of them can be true at a time   checking the upper limit should be sufficient   if scrollLeft  lt  oneRule upperLimit    provided that the conditions are defined in ascending order  first the lowest one  0 to 1000  and then 1000 to 2000 for example

User · Answer

This is another option        switch  true             case  value  gt  100                  do stuff              break           case  value  lt   100  amp  amp  value  gt  75                  do stuff              break           case  value  lt  50                 do stuff              break

User · Answer

Untested and unsure if this will work  but why not do a few if statements before  to set variables for the switch statement    var small  big   if scrollLeft  lt  1000         add some token to the page       call it small     switch    reference token       case  small        do stuff    break    case  big        do stuff     break

User · Answer

Updating the accepted answer  can t comment yet   As of 1 12 16 using the demo jsfiddle in chrome  switch-immediate is the fastest solution   Results  Time resolution  1 33     25ms  if-immediate  150878146     29ms  if-indirect  150878146    24ms  switch-immediate  150878146    128ms  switch-range  150878146    45ms  switch-range2  150878146    47ms  switch-indirect-array  150878146    43ms  array-linear-switch  150878146    72ms  array-binary-switch  150878146   Finished   1 04     25ms  if-immediate  1 21     29ms  if-indirect  1 00     24ms  switch-immediate  5 33    128ms  switch-range  1 88     45ms  switch-range2  1 96     47ms  switch-indirect-array  1 79     43ms  array-linear-switch  3 00     72ms  array-binary-switch

User · Answer

An alternative   var scrollleft   1000  switch  true        case  scrollleft  gt  1000         alert  gt          break      case  scrollleft  lt   1000         alert  lt          break       Demo  http   jsfiddle net UWYzr

User · Answer

When I looked at the solutions in the other answers I saw some things that I know are bad for performance  I was going to put them in a comment but I thought it was better to benchmark it and share the results  You can test it yourself  Below are my results  ymmv  normalized after the fastest operation in each browser  multiply the 1 0 time with the normalized value to get the absolute time in ms                         Chrome  Firefox Opera   MSIE    Safari  Node ------------------------------------------------------------------- 1 0 time               37ms    73ms    68ms   184ms    73ms    21ms if-immediate            1 0     1 0     1 0     2 6     1 0     1 0 if-indirect             1 2     1 8     3 3     3 8     2 6     1 0 switch-immediate        2 0     1 1     2 0     1 0     2 8     1 3 switch-range           38 1    10 6     2 6     7 3    20 9    10 4 switch-range2          31 9     8 3     2 0     4 5     9 5     6 9 switch-indirect-array  35 2     9 6     4 2     5 5    10 7     8 6 array-linear-switch     3 6     4 1     4 5    10 0     4 7     2 7 array-binary-switch     7 8     6 7     9 5    16 0    15 0     4 9   Test where performed on Windows 7 32bit with the folowing versions  Chrome 21 0 1180 89m  Firefox 15 0  Opera 12 02  MSIE 9 0 8112  Safari 5 1 7  Node was run on a Linux 64bit box because the timer resolution on Node js for Windows was 10ms instead of 1ms   if-immediate  This is the fastest in all tested environments  except in     drumroll MSIE   surprise  surprise   This is the recommended way to implement it   if  val  lt  1000      do something      else if  val  lt  2000      do something      else     if  val  lt  30000      do something      else   if-indirect  This is a variant of switch-indirect-array but with if-statements instead and performs much faster than switch-indirect-array in almost all tested environments    values      1000   2000      30000    if  val  lt  values 0        do something      else if  val  lt  values 1        do something      else     if  val  lt  values 29        do something      else   switch-immediate  This is pretty fast in all tested environments  and actually the fastest in MSIE  It works when you can do a calculation to get an index     switch  Math floor val 1000       case 0     do something    break    case 1     do something    break          case 29     do something    break      switch-range  This is about 6 to 40 times slower than the fastest in all tested environments except for Opera where it takes about one and a half times as long  It is slow because the engine has to compare the value twice for each case  Surprisingly it takes Chrome almost 40 times longer to complete this compared to the fastest operation in Chrome  while MSIE only takes 6 times as long  But the actual time difference was only 74ms in favor to MSIE at 1337ms        switch  true      case  0  lt   val  amp  amp   val  lt  1000      do something    break    case  1000  lt   val  amp  amp   val  lt  2000      do something    break          case  29000  lt   val  amp  amp   val  lt  30000      do something    break      switch-range2  This is a variant of switch-range but with only one compare per case and therefore faster  but still very slow except in Opera  The order of the case statement is important since the engine will test each case in source code order ECMAScript262 5 12 11  switch  true      case  val  lt  1000      do something    break    case  val  lt  2000      do something    break          case  val  lt  30000      do something    break      switch-indirect-array  In this variant the ranges is stored in an array  This is slow in all tested environments and very slow in Chrome   values  1000   2000     29000  30000    switch true      case  val  lt  values 0       do something    break    case  val  lt  values 1       do something    break          case  val  lt  values 29       do something    break      array-linear-search  This is a combination of a linear search of values in an array  and the switch statement with fixed values  The reason one might want to use this is when the values isn t known until runtime  It is slow in every tested environment  and takes almost 10 times as long in MSIE   values  1000   2000     29000  30000    for  sidx 0  slen values length  sidx  lt  slen    sidx      if  val  lt  values sidx   break     switch  sidx      case 0     do something    break    case 1     do something    break          case 29     do something    break      array-binary-switch  This is a variant of array-linear-switch but with a binary search  Unfortunately it is slower than the linear search  I don t know if it is my implementation or if the linear search is more optimized  It could also be that the keyspace is to small    values  0  1000   2000     29000  30000    while range      range   Math floor   smax - smin    2      sidx   smin   range    if   val  lt  values sidx      smax   sidx    else   smin   sidx       switch  sidx      case 0     do something    break          case 29     do something    break      Conclusion  If performance is important  use if-statements or switch with immediate values

[javascript] Switch statement for greater-than/less-than

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