js escape regex pattern characters

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const SPECIAL_CHARACTERS_EXPRESSION = /([.*+?^=!:${}()|\[\]\/\\])/g;

// Escapes regular expression pattern special characters in the indicated string.
//
const escapePattern = (pattern) => {
	return pattern.replace(SPECIAL_CHARACTERS_EXPRESSION, '\\$1');
};


// Usage example:

const pattern = escapePattern('.*');

console.log(pattern);  // '\.\*'

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// Hint: it is most optimal way to escape patterns represent as strings.

// Escapes regular expression pattern special characters in the indicated string.
//
const escapePattern = (pattern) => {
	let result = '';
  	for (let i = 0; i < pattern.length; ++i) {
    	const entry = pattern[i];
      	switch (entry) {
            case '^':
            case '$':
            case '*':
            case '+':
            case '?':
            case '.':
            case '{':
            case '}':
            case '(':
            case ')':
            case '[':
            case ']':
            case '=':
            case ':':
            case '!':
            case '|':
            case '/':
            case '\\':
                result += '\\' + entry;
                break;

            default:
                result += entry;
                break;
        }
    }
  	return result;
};


// Usage example:

const pattern = escapePattern('.*');

console.log(pattern);  // '\.\*'

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const SPECIAL_CHARACTERS = { '^': 1, '$': 1, '*': 1, '+': 1, '?': 1, '.': 1, '{': 1, '}': 1, '(': 1, ')': 1, '[': 1, ']': 1, '=': 1, ':': 1, '!': 1, '|': 1, '/': 1, '\\': 1 };

// Escapes regular expression pattern special characters in the indicated string.
//
const escapePattern = (pattern) => {
	let result = '';
  	for (let i = 0; i < pattern.length; ++i) {
    	const entry = pattern[i];
        result += (SPECIAL_CHARACTERS[entry] ? '\\' + entry : entry);
    }
  	return result;
};


// Usage example:

const pattern = escapePattern('.*');

console.log(pattern);  // '\.\*'

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const expression = new RegExp('\\.\\*', 'g');  // where: \\ will be converted to \ in the string literal
                                               //        . escaped by \. and * escaped by \*
                                               // Topic: https://dirask.com/questions/JavaScript-why-in-string-value-should-I-use-to-get-and-in-read-file-only-double-backslashes-in-strings-1b6xJ1

console.log(expression.source);  // '\\.\\*'      <---- source returns string literals with changed \ to \\ 

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const expression = /\.\*/g;      // . escaped by \. and * escaped by \*

console.log(expression.source);  // '\\.\\*'      <---- source returns string literals with changed \ to \\