Js Numbers | Table O Contents

Place the introducing line of text ie.) the ‘tagline’ here …

• Js Numbers | Table O Contents
  • Number()
    • Coercement
  • Boolean()
  • String()
  • Last Subtitle
  • Support
    • Patreon

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Number()

Hint. Javascript provides a primitive constructor for the Number object that makes a variable var immutable with respect to type.

Forcing or casting a variable’s type in Javascript may be performed with the primitive constructor for the Number object Number().

Coercement

A variable container declared with the primitive constructor for the Number object Number() may optionally accept numerical values masquerading as a string.

However, the Javascript engine will attempt to coerce the string into a number and if the string contains characters other than numerical digits, and if the Javascript engine is not comfortable with the resulting value when tested, a value of Not a Number, or NaN will be returned.

Note. Javascript also provides a primitive constructor for the Boolean object and the String object, as well.

As is the case for the primitive constructor for the Number object Number() …

Both the primitive constructor for the Boolean object Boolean() and the primitive constructor for the String object String() make a variable var immutable with respect to type.

Boolean()

Variable containers that have been created with the primitive constructor for the Boolean object Boolean() may only hold one of two distinct state.

The value placed into the variable container may be a true value, or the value placed into the variable container may be a false value.

Because the variable var was constructed with the primitive constructor for the Boolean object Boolean(), the type of value that can be placed into the variable container is the now immutably fixed bool type.

String()

When declared via the primitive constructor for the String object String(), a variable var returns false when tested if the string value provided is the empty string "", if the string value provided contains only the numeral zero (0) "0", or if the value provided is either undefined or null.

Note. When initializing a string at the time of declaration via the primitive constructor for the String object String(), the values of "NaN", "null", "undefined", "true", and "false" when tested will return true if operated upon by the toString method of the object String …!

In other words, the values declared for Number at the time of declaration when utilizing the primitive constructor for the Number object Number() may be changed to the different type string if operated upon by the toString method of the String object.

So, an odd case of explicitly changing an immutably declared variable var as to type does exist for Number when otherwise implicitly Javascript would simply return false when tested for string and NaN when tested for number.

Last Subtitle

More to come …

Note. The above synopsis was derived from an article written by Marijn Haverbeke [1].

1. Eloquent Javascript. Published by © 2012 Syncfusion.com.

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