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yeison.js
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yeison.js
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/********************************************************************
* TOKENIZER
********************************************************************/
// Tokenizer spec.
var Spec = [
// --------------------------------------
// Newline:
[/^\n/, null],
// --------------------------------------
// Whitespace:
[/^\s+/, null],
// --------------------------------------
// Symbols and delimiters:
[/^{/, '{'], // LeftBrace
[/^}/, '}'], // RightBrace
[/^\[/, '['], // LeftBracket
[/^\]/, ']'], // RightBracket
[/^,/, ','], // Comma
[/^\:/, ':'], // Colon
// --------------------------------------
// Keywords
[/^\btrue\b/, 'TRUE'],
[/^\bfalse\b/, 'FALSE'],
[/^\bnull\b/, 'NULL'],
// --------------------------------------
// Numbers:
[/^\-?\d+(\.\d+)?/, 'NUMBER'],
// --------------------------------------
// Double quoted String:
[/^"/, 'STRING'],
];
var _scannerString;
var _scannerCursor;
var _scannerLine = 1;
function _scanTokens(source) {
_scannerString = source;
_scannerCursor = 0; // track the position of each character
var tokens = [];
while (true) {
var token = _getNextToken();
if (token == null) {
break;
}
tokens.push(token);
}
tokens.push({
type: 'EOF',
value: null
});
return tokens;
}
/*
* Obtains next token.
*/
function _getNextToken() {
if (_scannerCursor >= _scannerString.length) {
return null;
}
var string = _scannerString.slice(_scannerCursor);
for (var i = 0; i < Spec.length; i++) {
var regexp = Spec[i][0];
var tokenType = Spec[i][1];
var tokenValue = _matchRegEx(regexp, string);
if (tokenValue == null) {
continue;
}
if (tokenValue == '\n') {
_scannerCursor++;
_scannerLine++;
continue;
}
if (tokenType == null) {
return _getNextToken();
}
// handle string token
if (tokenType == 'STRING') {
return _parseString();
}
return {
type: tokenType,
value: tokenValue
};
}
throw new SyntaxError('Unexpected token: "' + string[0] + '" at line ' + _scannerLine + '.');
}
/**
* Parses a string token.
*/
function _parseString() {
var lexeme = '';
var ch = '';
while (true) {
ch = _scannerString[_scannerCursor++];
if (ch == '"') {
break;
}
lexeme += ch;
}
return {
type: 'STRING',
value: lexeme
}
}
/*
* Matches a token for a regular expression.
*/
function _matchRegEx(regexp, string) {
var matched = regexp.exec(string);
if (matched == null) {
return null;
}
_scannerCursor += matched[0].length;
return matched[0];
}
// test the tokenizer
var tokens = _scanTokens('{"name": "Yeison", "age": 25, "isMale": true, "address": {"city": "Bogota", "country": "Colombia"}, "salary": 1000.50, "skills": ["C#", "JavaScript", "SQL"]}');
console.log(tokens);