ethers.js/packages/random/src.ts/browser-random.ts

"use strict";

import { arrayify } from "@ethersproject/bytes";

import { Logger } from "@ethersproject/logger";
import { version } from "./_version";
const logger = new Logger(version);

let anyGlobal: any = null;
try {
    anyGlobal = (window as any);
    if (anyGlobal == null) { throw new Error("try next"); }
} catch (error) {
    try {
        anyGlobal = (global as any);
        if (anyGlobal == null) { throw new Error("try next"); }
    } catch (error) {
        anyGlobal = { };
    }
}

let crypto: any = anyGlobal.crypto || anyGlobal.msCrypto;
if (!crypto || !crypto.getRandomValues) {

    logger.warn("WARNING: Missing strong random number source");

    crypto = {
        getRandomValues: function(buffer: Uint8Array): Uint8Array {
            return logger.throwError("no secure random source avaialble", Logger.errors.UNSUPPORTED_OPERATION, {
                operation: "crypto.getRandomValues"
            });
        }
    };
}

export function randomBytes(length: number): Uint8Array {
    if (length <= 0 || length > 1024 || (length % 1)) {
        logger.throwArgumentError("invalid length", "length", length);
    }

    const result = new Uint8Array(length);
    crypto.getRandomValues(result);
    return arrayify(result);
};