JavaScript and Open Data

3Data: Numbers and Strings

Developing and mastering the natural language has brought humankind a decisive advantage on our planet. Interpreting sounds or written signs is the first step. For a computer, this interpretation is not as soft and flexible as it is for human beings. In any real application, the first obstacle when reading a number or a piece of text is to correctly include it into the processing flow.

A single sign may mean different things: figures 7 and 10 can be numbers, but in “Ronaldo wears the 7, and Maradona the 10”, it is just nonsense to add 7 and 10.

Different words may mean the same thing: “Général De Gaulle” and “Charles de Gaulle”, or simply “Jean Pierre” and “Jean-Pierre”.

An illustration is given with the electoral data in Part 3: the difficulties in identifying a same single candidate when the name can be differently written out in two different files.

In this chapter, we visit “numbers” and “strings”, and in particular the use of:

• – concatenation operator (+), and comparisons with type string variables;
• – methods of the object String and String.prototype;
• – regular expressions and the object RegExp.

3.1. Handling numbers

3.1.1. Literal notation of type “number” variables

The literal notation of numbers can take several forms:

 4.2             encodes the real number 4.2
 -3e-5           encodes -0.00003 (scientific notation)
 0x0f            encodes 15 (hexadecimal notation)
 0x0g            SyntaxError: identifier starts immediately after numeric literal
 // only characters [0-9, a-f] ...