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Java Script Notes.
  Basic constrution is like "C++"
  Staements end in ';' though are not required
  comments start with // to end of line
  Multi-line and in-line comments   /* ..... */
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Output...

  console.log(...)   write to the browsers console

  Alert()     Various popup boxes (use sparingly, good for debugging)
  Confirm()
  Prompt()

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Variables

  Names are case sensitive.   X and x are different variables.
  They are dynamic types, so can be a boolean, integer, float, or string.
  Do not need to be declared.  If on declared they are global.

    y=5;
    y=y+1;

  let x = 30;       // scoped only in current block (preferred)
  var z = 50;       // scoped in current function

  true          boolean literals
  false
  undefined     special value

  'string'
  "John's Computer"
  name + "'s Computer"    // + is string concatenation
  "${name}'s Computer"    // embedding a variable


  var x = Math.floor(5/2);   // round down float to integer

  Math.random()   // random number from 0 (inclusive) to 1 (exclusive)
  var result = Math.floor(10 * Math.random());  // random integer, 0 to 9


  isNaN()   // is it not a number, eg may be a string or illegal result

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