How to swap two variables in JavaScript

Question

I have this two variables   var a   1      b   2    My question is how to swap them  Only this variables  not any objects

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Don t use the code below  It is not the recommended way to swap the values of two variables  simply use a temporary variable for that   It just shows a JavaScript trick   This solution uses no temporary variables  no arrays  only one addition  and it s fast  In fact  it is sometimes faster than a temporary variable  on several platforms   It works for all numbers  never overflows  and handles edge-cases such as Infinity and NaN   a   b    b a  0    It works in two steps     b a  0  sets b to the old value of a and yields 0 a   b   0 sets a to the old value of b

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You can use ES6 destructuring assignment like so   let a   10  let b   20    a  b     b  a     console log a  b      a   20  b   10

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We can use the IIFE to swap two value without extra parameter   x000D   x000D  var a   5  b  8  x000D  b    function a    x000D      return a  x000D    a  a b    x000D   x000D  document write  a      a     b      b   x000D   x000D   x000D

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I see kind of programming olympiad here  One more tricky one-line solution   b    function    a b  return arguments 0      a     Fiddle  http   jsfiddle net cherniv 4q226

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You could use a temporary swap variable or XOR   a   a   b b   a   b a   a   b   This is just a basic logical concept and works in every language that supports XOR operation   edit  see the Comments  Forgot to tell that this works for sure only with integer  Assumed  the integer variables from question s thread

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In ES6 now there is destructuring assignment and you can do   let a   1  let b   2   b  a     a  b      a   2  b   1

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Use a third variable like this   var a   1      b   2      c   a   a   b     must be first or a and b end up being both 1 b   c      DEMO - Using a third variable

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How could we miss these classic oneliners  var a   1  b   2 a     a b     b a    a    And  var a   1  b   2 a      b b a       The last one exposes global variable     but that should not matter as typical javascript convention is to use it as  dont care  variable

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Here s a one-liner  assuming a and b exist already and have values needing to be swapped   var c a  a b  b c    As  Kay mentioned  this actually performs better than the array way  almost 2x as fast

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It s very simple  use the ES6 array destructuring syntax which is  y  x     x  y  for more information consult this link https   developer mozilla org en-US docs Web JavaScript Reference Operators Destructuring assignment

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Destructing assignment is the best way to solve your problem   x000D   x000D  var a   1  var b   2    a  b     b  a    console log  After swap a     a    and b     b   x000D   x000D   x000D

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function A  B   b A  a B     parseInt a   parseInt b

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Swap using Bitwise  let a   10  let b   20  a    b  y    a  a    b    Single line Swap  using Array    a  b     b  a

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Till ES5  to swap two numbers  you have to create a temp variable and then swap it  But in ES6  its very easy to swap two numbers using array destructuring  See example   let x y   x y   2 3   console log x y           return 2 3   x y   y x   console log x y           return 3 2

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ES6 Destructuring   Using an array   a  b     b  a      my favorite  Using an object   a  b     a b  b a      not bad neither

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As your question was precious  Only this variables  not any objects     the answer will be also precious   var a   1          b   2  a a b  b a-b  a a-b    it s a trick And as  Rodrigo Assis said  it  can be shorter     b a  a b -b    Demo  http   jsfiddle net abdennour 2jJQ2

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ES6  Firefox and Chrome already support it  Destructuring Assignment Array Matching      x000D   x000D  let a   5  b   6  x000D   a  b     b  a   x000D  console log    a    b     x000D   x000D   x000D

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ES6  method  Since ES6  you can swap variables more elegantly  You can use destructuring assignment array matching  It   s simply  var a 10     b 20    a  b     b  a   console log a b     20 10

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We are able to swap var like this     var val1    117      val2   327   val2   val1-val2   console log val2   val1   val1-val2  console log val1   val2   val1 val2  console log val2

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You can now finally do   x000D   x000D  let a   5  let b   10    a  b     b  a      ES6  console log a  b   x000D   x000D   x000D

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let a   2  b   4   b  a     a  b     a more verbose approach would be  let a   2  b   4  a    a  b   b   a 0   a   a 1

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var a   5  var b   10   b    a  a   b  0     or b    a  a   b   b   b 0      or b    a  b   a   b 1   b   b 0     alert  a     a          b     b     remove or comment the 2   or s and run with the one set of code  http   jsfiddle net USdv8 57

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Single line swapping   a   a b  b   a b

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ES6 array destructuring is used to swap two variables  See example  var  x y   1 2    x y   y x     Easier way possible with    x     1 and y     2  But after destructuring  x is y  i e  2  and y is x  i e  1

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You can do this   var a   1      b   2      tmp  tmp   a  a   b  b   tmp    For readability and maintainability  this can t be beat  at least in JavaScript   Anybody maintaining the code  including you six months from now  will know exactly what s going on   Since these are integers  you can also use any number of clever tricks1 to swap without using a third variable  For instance you can use the bitwise xor operator    x000D   x000D  let a   1  b   2  x000D  a   a   b  x000D  b   a   b  x000D  a   a   b  x000D       x000D  console log  a is now    a   x000D  console log  b is now    b   x000D   x000D   x000D    This is called the XOR swap algorithm  Its theory of operation is described in this Wikipedia article   1 The competent programmer is fully aware of the limited size of his own skull  He therefore approaches his task with full humility  and avoids clever tricks like the plague    mdash  Edsger W  Dijkstra

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Here s a one-liner to swap the values of two variables  Given variables a and b   b    a  a   b  0     Demonstration below    x000D   x000D  var a 1  x000D      b 2  x000D      output document getElementById  output    x000D   x000D  output innerHTML   lt p gt Original    a      b   lt  p gt    x000D   x000D  b    a  a   b  0   x000D   x000D  output innerHTML    lt p gt Swapped    a      b   lt  p gt    x000D   lt div id  output  gt  lt  div gt  x000D   x000D   x000D

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Since ES6  you can also swap variables more elegantly     var a   1      b   2    a  b     b  a    console log  a    a   b    b      a  2 b  1

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Because I hear this method runs slower   b    a  a   b  0     If you plan on storing your vars in an object  or array   this function should work   function swapVars obj  var1  var2       let temp   obj var1       obj var1    obj var2       obj var2    temp      Usage   let test    a   test 1   b   test 2     console log test     output   a   test 1   b   test 2    swapVars test   a    b     console log test     output   a   test 2   b   test 1

[javascript] How to swap two variables in JavaScript

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