iconFont/node_modules/css-tree/lib/utils/names.js

const keywords = new Map();
const properties = new Map();
const HYPHENMINUS = 45; // '-'.charCodeAt()

export const keyword = getKeywordDescriptor;
export const property = getPropertyDescriptor;
export const vendorPrefix = getVendorPrefix;
export function isCustomProperty(str, offset) {
    offset = offset || 0;

    return str.length - offset >= 2 &&
           str.charCodeAt(offset) === HYPHENMINUS &&
           str.charCodeAt(offset + 1) === HYPHENMINUS;
}

function getVendorPrefix(str, offset) {
    offset = offset || 0;

    // verdor prefix should be at least 3 chars length
    if (str.length - offset >= 3) {
        // vendor prefix starts with hyper minus following non-hyper minus
        if (str.charCodeAt(offset) === HYPHENMINUS &&
            str.charCodeAt(offset + 1) !== HYPHENMINUS) {
            // vendor prefix should contain a hyper minus at the ending
            const secondDashIndex = str.indexOf('-', offset + 2);

            if (secondDashIndex !== -1) {
                return str.substring(offset, secondDashIndex + 1);
            }
        }
    }

    return '';
}

function getKeywordDescriptor(keyword) {
    if (keywords.has(keyword)) {
        return keywords.get(keyword);
    }

    const name = keyword.toLowerCase();
    let descriptor = keywords.get(name);

    if (descriptor === undefined) {
        const custom = isCustomProperty(name, 0);
        const vendor = !custom ? getVendorPrefix(name, 0) : '';
        descriptor = Object.freeze({
            basename: name.substr(vendor.length),
            name,
            prefix: vendor,
            vendor,
            custom
        });
    }

    keywords.set(keyword, descriptor);

    return descriptor;
}

function getPropertyDescriptor(property) {
    if (properties.has(property)) {
        return properties.get(property);
    }

    let name = property;
    let hack = property[0];

    if (hack === '/') {
        hack = property[1] === '/' ? '//' : '/';
    } else if (hack !== '_' &&
               hack !== '*' &&
               hack !== '$' &&
               hack !== '#' &&
               hack !== '+' &&
               hack !== '&') {
        hack = '';
    }

    const custom = isCustomProperty(name, hack.length);

    // re-use result when possible (the same as for lower case)
    if (!custom) {
        name = name.toLowerCase();
        if (properties.has(name)) {
            const descriptor = properties.get(name);
            properties.set(property, descriptor);
            return descriptor;
        }
    }

    const vendor = !custom ? getVendorPrefix(name, hack.length) : '';
    const prefix = name.substr(0, hack.length + vendor.length);
    const descriptor = Object.freeze({
        basename: name.substr(prefix.length),
        name: name.substr(hack.length),
        hack,
        vendor,
        prefix,
        custom
    });

    properties.set(property, descriptor);

    return descriptor;
}