gobbleBinaryOp() {
		this.gobbleSpaces();
		let to_check = this.expr.substr(this.index, Jsep.max_binop_len);
		let tc_len = to_check.length;

		while (tc_len > 0) {
			// Don't accept a binary op when it is an identifier.
			// Binary ops that start with a identifier-valid character must be followed
			// by a non identifier-part valid character
			if (Jsep.binary_ops.hasOwnProperty(to_check) && (
				!Jsep.isIdentifierStart(this.code) ||
				(this.index + to_check.length < this.expr.length && !Jsep.isIdentifierPart(this.expr.charCodeAt(this.index + to_check.length)))
			)) {
				this.index += tc_len;
				return to_check;
			}
			to_check = to_check.substr(0, --tc_len);
		}
		return false;
	}
Search for the operation portion of the string (e.g. `+`, `===`)
Start by taking the longest possible binary operations (3 characters: `===`, `!==`, `>>>`)
and move down from 3 to 2 to 1 character until a matching binary operation is found
then, return that binary operation
@returns {string|boolean}