node_modules/@sinonjs/commons/lib/class-name.js

"use strict";

var functionName = require("./function-name");

module.exports = function className(value) {
    return (
        (value.constructor && value.constructor.name) ||
        // The next branch is for IE11 support only:
        // Because the name property is not set on the prototype
        // of the Function object, we finally try to grab the
        // name from its definition. This will never be reached
        // in node, so we are not able to test this properly.
        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name
        (typeof value.constructor === "function" &&
            /* istanbul ignore next */
            functionName(value.constructor)) ||
        null
    );
};