Summary

  • All comparison operators, including greater/less than, greater/less than or equals, equals, and not equals, return a boolean value, either true or false.

  • JavaScript uses lexicographical order to do string comparison.

  • When comparing values of different types, JavaScript converts the values to numbers.

  • A regular equality check == cannot differentiate 0 from false. This happens because operands of different types are converted to numbers by the equality operator ==. An empty string, just like false, becomes a zero. Thus, we use a strict equality operator === to check the equality without type conversion. There is also a strict non-equality operator !== analogous to !=.

  • For a non-strict check ==, null and undefined equals each other, but not any other value. For maths and other comparisons like <, >, <=, and >=, null becomes 0 while undefined becomes NaN. To sum up, treat any comparison with undefined/null except the strict equality === with exceptional care. Don’t use comparisons <, >, <=, and >= with a variable which may be null/undefined.

Tasks

  • Comparisons

    5 > 4 // true
"apple" > "pineapple" // false
"2" > "12" // true
undefined == null // true
undefined === null //false
null == "\n0\n" //false
null === +"\n0\n" //false

References