Switch on ranges of integers in JavaScript

Question

I want to do something like this      switch  this dealer            case 1-4                  Do something              break          case 5-8                  Do something              break          case 9-11                  Do something              break          default              break          What is the right syntax for this  Is it possible in JavaScript   So this dealer is an integer  and if it s between those values  do something

User · Answer

This does not require a switch statement  It is clearer  more concise  faster  and optimises better  to use if else statements     var d   this dealer  if  1  lt   d  amp  amp  d  lt   11       making sure in range 1  11     if  d  lt   4            alert  1 to 4          else if  d  lt   8            alert  5 to 8          else           alert  9 to 11            else       alert  not in range        Speed test   I was curious about the overhead of using a switch instead of the simpler if   else     so I put together a jsFiddle to examine it    http   jsfiddle net 17x9w1eL    Chrome  switch was around 70  slower than if else Firefox  switch was around 5  slower than if else IE  switch was around 5  slower than if else Safari  switch was around 95  slower than if else   Notes   Assigning to the local variable is optional  especially if your code is going to be automatically optimised later   For numeric ranges  I like to use this kind of construction     if  1  lt   d  amp  amp  d  lt   11              because to me it reads closer to the way you would express a range in maths  1  lt   d  lt   11   and when I m reading the code  I can read that as  if d is between 1 and 11    Clearer  A few people don t think this is clearer   I d say it is not less clear as the structure is close to identical to the switch option   The main reason it is clearer is that every part of it is readable and makes simple intuitive sense   My concern  with  switch  true    is that it can appear to be a meaningless line of code  Many coders  reading that will not know what to make of it   For my own code  I m more willing to use obscure structures from time to time  but if anyone else will look at it  I try to use clearer constructs  I think it is better to use the constructs for what they are intended   Optimisation  In a modern environment  code is often going to be minified for production  so you can write clear concise code  with readable variable names and helpful comments  There s no clear reason to use switch in this way   I also tried putting both constructs through a minifier  The if else structure compresses well  becoming a single short expression using nested ternary operators  The switch statement when minified remains a switch  complete with  switch    case  and  break  tokens  and as a result is considerably longer in code   How switch true  works  I think  switch true  is obscure  but it seems some people just want to use it  so here s an explanation of why it works     A switch case statement works by matching the part in the switch with each case  and then executing the code on the first match  In most use cases  we have a variable or non-constant expression in the switch  and then match it    With  switch true   we will find the first expression in the case statements that is true  If you read  switch  true   as  find the first expression that is true   the code feels more readable

User · Answer

Here is another way I figured it out   const x   this dealer  switch  true        case  x  lt  5           alert  less than five            break      case  x  lt  9           alert  between 5 and 8            break      case  x  lt  12           alert  between 9 and 11            break      default          alert  none            break

User · Answer

If you are trying to do something fast  efficient and readable  use a standard if   then   else structure like this   var d   this dealer  if  d  lt  12        if  d  lt  5            alert  less than five         else if  d  lt  9            alert  between 5 and 8         else          alert  between 9 and 11           else      alert  none        If you want to obfuscate it and make it awful  but small   try this   var d this dealer d lt 12  d lt 5 alert  less than five   d lt 9 alert  between 5 and 8   alert  between 9 and 11    alert  none      BTW  the above code is a JavaScript if   then   else shorthand statement  It is a great example of how NOT to write code unless obfuscation or code minification is the goal  Be aware that code maintenance can be an issue if written this way  Very few people can easily read through it  if at all  The code size  however  is 50  smaller than the standard if   then   else without any loss of performance  This means that in larger codebases  minification like this can greatly speed code delivery across bandwidth constrained or high latency networks   This  however  should not be considered a good answer  It is just an example of what CAN be done  not what SHOULD be done

User · Answer

switch this dealer            case 1          case 2          case 3          case 4                 Do something              break          case 5          case 6          case 7          case 8                 Do something              break          default              break          If you don t like the succession of cases  simply go for if else if else statements

User · Answer

A more readable version of the ternary might look like    var x   this dealer  alert t  lt  1    t  gt  11      none        t  lt  5      less than five        t  lt   8      between 5 and 8       Between 9 and 11

User · Answer

No  this is not possible  The closest you can get is     switch this dealer        case 1      case 2      case 3      case 4                           DO SOMETHING         break      case 5      case 6      case 7      case 8                           DO SOMETHING        break    But this very unwieldly    For cases like this it s usually better just to use a if else if structure

User · Answer

function sequentialSizes val     var answer         switch  val   case 1  case 2  case 3  case 4    answer  Less than five     break  case 5  case 6  case 7  case 8    answer  less than 9     break  case 8  case 10  case 11    answer  More than 10     break      return answer          Change this value to test you code to confirm    sequentialSizes 1

User · Answer

Incrementing on the answer by MarvinLabs to make it cleaner   var x   this dealer  switch  true        case  x  lt  5           alert  less than five            break      case  x  lt  9           alert  between 5 and 8            break      case  x  lt  12           alert  between 9 and 11            break      default          alert  none            break      It is not necessary to check the lower end of the range because the break statements will cause execution to skip remaining cases  so by the time execution gets to checking e g   x  lt  9  we know the value must be 5 or greater   Of course the output is only correct if the cases stay in the original order  and we assume integer values  as stated in the question  - technically the ranges are between 5 and 8 999999999999 or so since all numbers in js are actually double-precision floating point numbers   If you want to be able to move the cases around  or find it more readable to have the full range visible in each case statement  just add a less-than-or-equal check for the lower range of each case   var x   this dealer  switch  true        case  x  lt  5           alert  less than five            break      case  x  gt   5  amp  amp  x  lt  9           alert  between 5 and 8            break      case  x  gt   9  amp  amp  x  lt  12           alert  between 9 and 11            break      default          alert  none            break      Keep in mind that this adds an extra point of human error - someone may try to update a range  but forget to change it in both places  leaving an overlap or gap that is not covered  e g  here the case of 8 will now not match anything when I just edit the case that used to match 8       case  x  gt   5  amp  amp  x  lt  8           alert  between 5 and 7            break      case  x  gt   9  amp  amp  x  lt  12           alert  between 9 and 11            break

User · Answer

If you need check ranges you are probably better off with if and else if statements  like so   if  range  gt  0  amp  amp  range  lt  5                else if  range  gt  5  amp  amp  range  lt  9                else          Fall through     A switch could get large on bigger ranges

[javascript] Switch on ranges of integers in JavaScript

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