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
StringandString.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] ...