JavaScript: Data type conversion by itself

Open the Chrome JavaScript console, and try the following code.

  0 == false;    // true
  0 == ' ';      // true
  0 + 0 == false + ' '; // ???

  0 == ' '      // true
  0 == '0'      // true
  0 + 0 == ' ' + '0'  // ???

  false + '' == 'false' //???
  false == 'false';     //???

  false + '0' == false + 0; // ???

  undefined == null; //???
  undefined === null; //???
  undefined == null + null //???

Line 3 returns false.
Line 7 returns true.
Line 9 returns true.
Line 10 returns false
...
So, be careful to choose between == and ===.