JavaScript Salesforce ID Check & Expansion

sales-force-id-validator.ts

class SalesForceIdValidator {
    private ID_REGEX = /^[0-9a-zA-Z]{15}([0-9a-zA-Z]{3})?$/;
    private ID_EXPAND_ARRAY = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','0','1','2','3','4','5'];

    constructor(private id: string) {}

    public IsValid(): boolean {
        if (!this.id) {
            console.warn('[SalesForceIdValidator] id is empty');
            return false;
        }
        if (!this.ID_REGEX.test(this.id)) {
            console.warn('[SalesForceIdValidator] id is invalid');
            return false;
        }

        if (this.id.length === 18) {
            if (!this._validateCheckSum()) {
                console.warn('[SalesForceIdValidator] checksum is invalid');
                return false;
            }            
        }
        return true;
    }

    private _validateCheckSum() {
        return this.id.endsWith(this._getCheckSum());
    }

    private _getCheckSum() {
        var chunks = [this.id.substr(0, 5), this.id.substr(5, 5), this.id.substr(10, 5)];
        let chunkBits = ['','',''];

        for (var i=0;i<chunks[0].length;i++) chunkBits[0] = (/[A-Z]/.test(chunks[0].substr(i, 1)) ? '1' : '0') + chunkBits[0];
        for (var i=0;i<chunks[1].length;i++) chunkBits[1] = (/[A-Z]/.test(chunks[1].substr(i, 1)) ? '1' : '0') + chunkBits[1];
        for (var i=0;i<chunks[2].length;i++) chunkBits[2] = (/[A-Z]/.test(chunks[2].substr(i, 1)) ? '1' : '0') + chunkBits[2];

        const ID_EXPAND_ARRAY = this.ID_EXPAND_ARRAY;
        return ID_EXPAND_ARRAY[parseInt(chunkBits[0], 2)] + ID_EXPAND_ARRAY[parseInt(chunkBits[1], 2)] + ID_EXPAND_ARRAY[parseInt(chunkBits[2], 2)];
    }
}