src/pattern-matcher.js
function isEscaped(str, index) {
    let escaped = false
    for (let i = index - 1; i >= 0 && str.charCodeAt(i) === 0x5c; --i) {
        escaped = !escaped
    }
    return escaped
}
function isEscaped(str, index) {
    let escaped = false
    for (let i = index - 1; i >= 0 && str.charCodeAt(i) === 0x5c; --i) {
        escaped = !escaped
    }
    return escaped
}
Check whether a given character is escaped or not.
@param {string} str The string to check.
@param {number} index The location of the character to check.
@returns {boolean} `true` if the character is escaped.