function isArrayIndex()

in packages/web-components/fast-foundation/src/di/di.ts [2087:2116]

• 30 lines of code
• 12 McCabe index (conditional complexity)

function isArrayIndex(value: unknown): value is number | string {
    switch (typeof value) {
        case "number":
            return value >= 0 && (value | 0) === value;
        case "string": {
            const result = isNumericLookup[value];
            if (result !== void 0) {
                return result;
            }
            const length = value.length;
            if (length === 0) {
                return (isNumericLookup[value] = false);
            }
            let ch = 0;
            for (let i = 0; i < length; ++i) {
                ch = value.charCodeAt(i);
                if (
                    (i === 0 && ch === 0x30 && length > 1) /* must not start with 0 */ ||
                    ch < 0x30 /* 0 */ ||
                    ch > 0x39 /* 9 */
                ) {
                    return (isNumericLookup[value] = false);
                }
            }
            return (isNumericLookup[value] = true);
        }
        default:
            return false;
    }
}