/* eslint-disable no-template-curly-in-string */
/* eslint-disable new-cap */
/* *************************************************************************************
* copyright: Copyright (c) 2021 Lowell D. Thomas, all rights reserved
* license: BSD-2-Clause (https://opensource.org/licenses/BSD-2-Clause)
* ********************************************************************************* */This module demonstrates the replace() function.
It is roughly equivalent to the JavaScript string String.replace(regex, string | function) function
(It follows closely the MDN description.)
If the global flag g is not set, only the first matched phrase is replaced.
If the global flag g is set, all matched phrases will be replaced.
If the sticky flag y is set, all matched ‘consecutive’ phrases will be replaced.
If the unicode flag u is set, an exception will be thrown. replace() only works on strings, not character code arrays.
Consider something like:
exp = new apgExp('rule = "abc"\n);
str = "---abc---";
restr = "xyz";
let re = exp.replace(str, restr);
This will replace abc with xyz and return the result in re.
The string restr may contain replacement patterns.
$$ - insert the character $ - is the escape sequence for the $ character
$` - insert the prefix to the matched pattern
$& - insert the matched pattern
$' - insert the suffix of the matched pattern
${name} - insert the last match to the rule "name"
restr may also be a user-written function of the form
let restr = function(result, exp){
// result is the result object from the pattern match
// exp is the "last match" object
}
There is quite a bit of redundancy here with both the result object and the apg-exp object being passed to the
replacement function. However, this provides the user with a great deal of flexibility in what might be the
most convenient way to create the replacement. Also, the apg-exp object has the AST which is a powerful
translation tool for really tough replacement jobs. We’ll see some examples of that elsewhere.
(function replace() {
try {
const apgJs = require('apg-js');
const { apgExp } = apgJs;
let grammar = '';
let exp;
let flags;
let str;
let restr;
let patternString;
grammar += 'rule = ABC / XYZ\n';
grammar += 'ABC = A BC\n';
grammar += 'A = "a"\n';
grammar += 'BC = "bc"\n';
grammar += 'XYZ = X YZ\n';
grammar += 'X = "x"\n';
grammar += 'YZ = "yz"\n';
flags = '';
exp = new apgExp(grammar, flags);
console.log();
console.log('Demonstrate replacing matched phrases.');
console.log();
console.log(` grammar: ${exp.source}`);
str = '---abc---xyz---ABC---';
console.log(' : simple replacement of a single match');
console.log(` flags: '${exp.flags}'`);
console.log(` input: ${str}`);
restr = exp.replace(str, 'replace abc with this');
console.log(`replaced: ${restr}`);
flags = 'g';
exp = new apgExp(grammar, flags);
console.log();
console.log(' : global replacement of all matches');
console.log(` flags: '${exp.flags}'`);
console.log(` input: ${str}`);
restr = exp.replace(str, '555');
console.log(`replaced: ${restr}`);
flags = '';
str = '<<<abc>>>';
patternString = "$'---$`";
exp = new apgExp(grammar, flags);
console.log();
console.log(" : use 'pattern' string replacement");
console.log(` flags: '${exp.flags}'`);
console.log(` input: ${str}`);
console.log(` pattern: ${patternString}`);
restr = exp.replace(str, patternString);
console.log(`replaced: ${restr}`);
flags = '';
patternString = '${BC}';
exp = new apgExp(grammar, flags);
console.log();
console.log(" : use rule 'pattern' string replacement");
console.log(` flags: '${exp.flags}'`);
console.log(` input: ${str}`);
console.log(` pattern: ${patternString}`);
restr = exp.replace(str, patternString);
console.log(`replaced: ${restr}`);
flags = '';
const patternFunc = function patternFunc(result, expArg) {
let a;
let bc;
let restrr;
if (result.rules.ABC) {
a = result.rules.A[0].phrase;
bc = result.rules.BC[0].phrase;
restrr = bc + a;
} else if (expArg['${XYZ}']) {
a = expArg['${X}'];
bc = expArg['${YZ}'];
restrr = bc + a;
}
return restrr;
};
exp = new apgExp(grammar, flags);
console.log();
console.log(' : function replacement - manipulate matched sub-rules for string replacement');
console.log(` flags: '${exp.flags}'`);
console.log(` input: ${str}`);
restr = exp.replace(str, patternFunc);
console.log(`replaced: ${restr}`);
str = '---xyz---';
console.log(` input: ${str}`);
restr = exp.replace(str, patternFunc);
console.log(`replaced: ${restr}`);
flags = 'u';
exp = new apgExp(grammar, flags);
console.log();
console.log(" : can't do replace with the unicode, 'u', flag set");
console.log(` flags: '${exp.flags}'`);
console.log(` input: ${str}`);
restr = exp.replace(str, '555');
} catch (e) {
console.log(`EXCEPTION: ${e.message}`);
}
})();