Loops in JavaScript

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Loops in JavaScript

• Pratik Desai

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The FOR loop

• Loop used to run the same piece of code again and
  again.
• FOR loop runs a code specific number of times.
• Used when we know in advance, how many times the
  script should run.

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The FOR loop..

• Syntaxfor(initializationconditioniteration)
  code to be executed
• Initialization of counter, which counts the
  number of times the loop is run, i.e. the code is
  executed.
• Iteration incrementing the counter by one..
• Incrementing gt ii1 or i

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The FOR loop

• e.g. var total0var i0for (i0ilt6i)
  document.write("The number is " i)
  document.write("ltbr /gt")totaltotali
  document.write(The Total is total)
• ResultThe number is 0 The number is 1 The
  number is 2 The number is 3 The number is 4
  The number is 5 The Total is 15

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The FOR Loop

• Two ways to write the loop..
• for(var i0iltXi)code
• for(var i1iltXi)code
• The number of times loop is repeated is the same.
  
• Output may differ though...

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The WHILE Loop

• Used when you want the loop to execute and
  continue executing while the specified condition
  is true. 
• Syntaxwhile (condition) code to be executed
  

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The WHILE Loop

• e.g.var i0 while (ilt6) document.write("The
  number is " i) document.write("ltbr
  /gt")ii1
• ResultThe number is 0The number is 1The
  number is 2The number is 3The number is 4The
  number is 5

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The DOWHILE Loop

• Variant of WHILE loop.
• Executed at least once (even though condition is
  false), and then repeat the loop as long as
  specified condition is true.
• Syntaxdocode to be executedwhile
  (condition)

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The DOWHILE Loop

• e.g.var i0do document.write("The number
  is " i) document.write("ltbr /gt")ii1
  while (ilt0)
• ResultThe number is 0
• Notice that loop executed once even though
  condition is false.