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[英]Why the variable is undefined in the method but it is not in the constructor in Typescript
[英]Typescript: undefined is not a constructor
我有一個正在與Mocha / Chai測試的克隆函數:
export function clone(source: any): any {
let output = {};
if (isObject(source)) {
(<any>Object).keys(source).forEach(key => {
(<any>Object).assign(output, { [key]: source[key] });
});
}
return output;
}
這是測試:
let obj = {
a: [
{
a: 3,
b: 5,
c: [6, 8]
}
]
};
it('clone(object) creates deep clone', () => {
let cloned = ObjectHelper.clone(obj);
expect(cloned.a[0].a).to.equal(3);
expect(cloned.a[0].c[1]).to.equal(6);
});
但是我得到這個錯誤:
undefined is not a constructor (evaluating 'Object.assign(output, (_a = {}, _a[key] = source[key], _a))')
這只會在測試中失敗,而不會在瀏覽器中失敗。
業力配置:
module.exports = function(config) {
config.set({
/*
* Enable or disable watching files and executing the tests whenever
* one of the files in the 'files' field is changed.
*/
autoWatch: true,
/*
* The root path location that will be used to resolve all relative
* paths defined in 'files' and 'exclude'.
*/
basePath: '',
/*
* List of browsers to launch and capture tests in. In order to use a
* specified browser, you must npm install the corresponding
* karma-***-launcher.
* http://karma-runner.github.io/0.13/config/browsers.html
*/
browsers: ['PhantomJS'],
// Enable or disable colors in the output (reporters and logs)
colors: true,
// List of files/patterns to exclude from loaded files
exclude: [],
/*
* The files array determines which files are included in the browser
* and which files are watched and served by Karma. The order of patterns
* determines the order in which files are included in the browser.
* http://karma-runner.github.io/0.13/config/files.html
*/
files: [
'src/**/*.spec.ts'
],
/*
* List of test frameworks you want to use. For example, if you want to
* use mocha, chai, and sinon, you'll need to npm install their
* corresponding karma-*** modules and include them in the list of plugins
* as well as below.
*/
frameworks: ['mocha', 'chai', 'sinon'],
logLevel: config.LOG_INFO,
/*
* By default, Karma loads all sibling NPM modules which have a name
* starting with karma-*. You can also explicitly list plugins you want
* to load via the plugins configuration setting.
*/
plugins: [
'karma-*'
],
// The port where the Karma web server will be listening.
port: 9876,
/*
* A map of preprocessors to use. Requires the corresponding karma-*
* npm module to be npm installed and added to the 'plugins' field.
*/
preprocessors: {
'src/**/*.spec.ts': ['webpack']
},
/*
* A list of reporters to use to display the test results. In order to
* use the karma-mocha-reporter, you must npm install the module and
* include it in the list of plugins.
*/
reporters: ['mocha'],
/*
* If true, Karma will start and capture all configured browsers, run
* tests and then exit with an exit code of 0 or 1 depending on whether
* all tests passed or any tests failed.
*/
singleRun: false,
/*
* This field is necessary because we are using webpack as a preprocessor.
* You will need to specify the webpack configuration (although in this
* case, we are simply leveraging the existing webpack.config.js file).
*
* If you have a different webpack.config.js file that's used for testing
* purposes, you can specify that here.
*/
webpack: {
module: webpackConfig.module,
resolve: webpackConfig.resolve
}
});
};
我認為您的問題是您的環境沒有實現Object.create
,即您沒有ES6
功能。
這是針對PhantomJs的polyfil: https ://www.npmjs.com/package/phantomjs-polyfill-object-assign
另外,您可以將它以typescript形式進行過濾(只是這樣,您就不必將其強制轉換為any
):
interface ObjectConstructor {
keys(o: any): string[];
assign(target: any, ...sources: any[]): any;
}
如果將ES6
用作編譯器的目標,則不需要此polyfil,因為它已經內置。
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