lib/rules/no-useless-escape.js
function check(node) {
            const isTemplateElement = node.type === "TemplateElement";

            if (
                isTemplateElement &&
                node.parent &&
                node.parent.parent &&
                node.parent.parent.type === "TaggedTemplateExpression" &&
                node.parent === node.parent.parent.quasi
            ) {

                // Don't report tagged template literals, because the backslash character is accessible to the tag function.
                return;
            }

            if (typeof node.value === "string" || isTemplateElement) {

                /*
                 * JSXAttribute doesn't have any escape sequence: https://facebook.github.io/jsx/.
                 * In addition, backticks are not supported by JSX yet: https://github.com/facebook/jsx/issues/25.
                 */
                if (node.parent.type === "JSXAttribute" || node.parent.type === "JSXElement" || node.parent.type === "JSXFragment") {
                    return;
                }

                const value = isTemplateElement ? node.value.raw : node.raw.slice(1, -1);
                const pattern = /\\[^\d]/gu;
                let match;

                while ((match = pattern.exec(value))) {
                    validateString(node, match);
                }
            } else if (node.regex) {
                parseRegExp(node.regex.pattern)

                    /*
                     * The '-' character is a special case, because it's only valid to escape it if it's in a character
                     * class, and is not at either edge of the character class. To account for this, don't consider '-'
                     * characters to be valid in general, and filter out '-' characters that appear in the middle of a
                     * character class.
                     */
                    .filter(charInfo => !(charInfo.text === "-" && charInfo.inCharClass && !charInfo.startsCharClass && !charInfo.endsCharClass))

                    /*
                     * The '^' character is also a special case; it must always be escaped outside of character classes, but
                     * it only needs to be escaped in character classes if it's at the beginning of the character class. To
                     * account for this, consider it to be a valid escape character outside of character classes, and filter
                     * out '^' characters that appear at the start of a character class.
                     */
                    .filter(charInfo => !(charInfo.text === "^" && charInfo.startsCharClass))

                    // Filter out characters that aren't escaped.
                    .filter(charInfo => charInfo.escaped)

                    // Filter out characters that are valid to escape, based on their position in the regular expression.
                    .filter(charInfo => !(charInfo.inCharClass ? REGEX_GENERAL_ESCAPES : REGEX_NON_CHARCLASS_ESCAPES).has(charInfo.text))

                    // Report all the remaining characters.
                    .forEach(charInfo => report(node, charInfo.index, charInfo.text));
            }

        }
function check(node) {
            const isTemplateElement = node.type === "TemplateElement";

            if (
                isTemplateElement &&
                node.parent &&
                node.parent.parent &&
                node.parent.parent.type === "TaggedTemplateExpression" &&
                node.parent === node.parent.parent.quasi
            ) {

                // Don't report tagged template literals, because the backslash character is accessible to the tag function.
                return;
            }

            if (typeof node.value === "string" || isTemplateElement) {

                /*
                 * JSXAttribute doesn't have any escape sequence: https://facebook.github.io/jsx/.
                 * In addition, backticks are not supported by JSX yet: https://github.com/facebook/jsx/issues/25.
                 */
                if (node.parent.type === "JSXAttribute" || node.parent.type === "JSXElement" || node.parent.type === "JSXFragment") {
                    return;
                }

                const value = isTemplateElement ? node.value.raw : node.raw.slice(1, -1);
                const pattern = /\\[^\d]/gu;
                let match;

                while ((match = pattern.exec(value))) {
                    validateString(node, match);
                }
            } else if (node.regex) {
                parseRegExp(node.regex.pattern)

                    /*
                     * The '-' character is a special case, because it's only valid to escape it if it's in a character
                     * class, and is not at either edge of the character class. To account for this, don't consider '-'
                     * characters to be valid in general, and filter out '-' characters that appear in the middle of a
                     * character class.
                     */
                    .filter(charInfo => !(charInfo.text === "-" && charInfo.inCharClass && !charInfo.startsCharClass && !charInfo.endsCharClass))

                    /*
                     * The '^' character is also a special case; it must always be escaped outside of character classes, but
                     * it only needs to be escaped in character classes if it's at the beginning of the character class. To
                     * account for this, consider it to be a valid escape character outside of character classes, and filter
                     * out '^' characters that appear at the start of a character class.
                     */
                    .filter(charInfo => !(charInfo.text === "^" && charInfo.startsCharClass))

                    // Filter out characters that aren't escaped.
                    .filter(charInfo => charInfo.escaped)

                    // Filter out characters that are valid to escape, based on their position in the regular expression.
                    .filter(charInfo => !(charInfo.inCharClass ? REGEX_GENERAL_ESCAPES : REGEX_NON_CHARCLASS_ESCAPES).has(charInfo.text))

                    // Report all the remaining characters.
                    .forEach(charInfo => report(node, charInfo.index, charInfo.text));
            }

        }
function check ( node ) { const isTemplateElement = node . type === "TemplateElement" ; if ( isTemplateElement && node . parent && node . parent . parent && node . parent . parent . type === "TaggedTemplateExpression" && node . parent === node . parent . parent . quasi ) { // Don't report tagged template literals, because the backslash character is accessible to the tag function. return ; } if ( typeof node . value === "string" || isTemplateElement ) { /*
                 * JSXAttribute doesn't have any escape sequence: https://facebook.github.io/jsx/.
                 * In addition, backticks are not supported by JSX yet: https://github.com/facebook/jsx/issues/25.
                 */ if ( node . parent . type === "JSXAttribute" || node . parent . type === "JSXElement" || node . parent . type === "JSXFragment" ) { return ; } const value = isTemplateElement ? node . value . raw : node . raw . slice ( 1 , - 1 ) ; const pattern = / \\[^\d] / gu ; let match ; while ( ( match = pattern . exec ( value ) ) ) { validateString ( node , match ) ; } } else if ( node . regex ) { parseRegExp ( node . regex . pattern ) /*
                     * The '-' character is a special case, because it's only valid to escape it if it's in a character
                     * class, and is not at either edge of the character class. To account for this, don't consider '-'
                     * characters to be valid in general, and filter out '-' characters that appear in the middle of a
                     * character class.
                     */ . filter ( charInfo => ! ( charInfo . text === "-" && charInfo . inCharClass && ! charInfo . startsCharClass && ! charInfo . endsCharClass ) ) /*
                     * The '^' character is also a special case; it must always be escaped outside of character classes, but
                     * it only needs to be escaped in character classes if it's at the beginning of the character class. To
                     * account for this, consider it to be a valid escape character outside of character classes, and filter
                     * out '^' characters that appear at the start of a character class.
                     */ . filter ( charInfo => ! ( charInfo . text === "^" && charInfo . startsCharClass ) ) // Filter out characters that aren't escaped. . filter ( charInfo => charInfo . escaped ) // Filter out characters that are valid to escape, based on their position in the regular expression. . filter ( charInfo => ! ( charInfo . inCharClass ? REGEX_GENERAL_ESCAPES : REGEX_NON_CHARCLASS_ESCAPES ) . has ( charInfo . text ) ) // Report all the remaining characters. . forEach ( charInfo => report ( node , charInfo . index , charInfo . text ) ) ; } }
Checks if a node has an escape.

@param {ASTNode} node - node to check.
@returns {void}
Checks if a node has an escape .