Mastering JavaScript

Chapter 1
You can also omit all three of these expressions and write for loops. One interesting
idiom used frequently is to use for loops with empty statements. The following loop
is used to set all the elements of the array to 100. Notice how there is no body to the
for-loop:
var arr = [10, 20, 30];
// Assign all array values to 100
for (i = 0; i < arr.length; arr[i++] = 100);
console.log(arr);
The empty statement here is just the single that we see after the for loop statement.
The increment factor also modifies the array content. We will discuss arrays later in
the book, but here it's sufficient to see that the array elements are set to the 100 value
within the loop definition itself.
Equality
JavaScript offers two modes of equality—strict and loose. Essentially, loose equality
will perform the type conversion when comparing two values, while strict equality
will check the values without any type conversion. A strict equality check is
performed by === while a loose equality check is performed by ==.
ECMAScript 6 also offers the Object.is method to do a strict equality check like ===.
However, Object.is has a special handling for NaN: -0 and +0. When NaN===NaN
and NaN==NaN evaluates to false, Object.is(NaN,NaN) will return true.
Strict equality using ===
Strict equality compares two values without any implicit type conversions. The
following rules apply:
• If the values are of a different type, they are unequal.
• For non-numerical values of the same type, they are equal if their values are
the same.
• For primitive numbers, strict equality works for values. If the values are the
same, === results in true. However, a NaN doesn't equal to any number and
NaN=== would be a false.
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