js escape regex pattern characters

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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);  // '\.\*'