Sometimes you might want to call a function in Javascript but check if the function exists before calling it. This is very simple and is covered in this post. You can test if a function exists in Javascript by
ItemAlreadyExists所创建的资源已存在。无 ItemNotFound所请求的资源不存在。无 MemoryLimitReached已达到内存限制。 无法完成作。无 NotImplemented所请求的功能未实现。这可能意味着 API 处于预览状态,或仅在特定平台 ((例如仅联机) )上受支持。 有关详细信息,请参阅 Office 外接程序的 Office 客户端应用程序和...
7. `averageBy`:数组对象属性平均数 此代码段将获取数组对象属性的平均值 代码语言:javascript 复制 constaverageBy=(arr,fn)=>arr.map(typeoffn==='function'?fn:val=>val[fn]).reduce((acc,val)=>acc+val,0)/arr.length;averageBy([{n:4},{n:2},{n:8},{n:6}],o=>o.n);// 5averageBy...
function checkePlugs(pluginname) { var f = "-" var plugins = navigator.plugins; if (plugins.length > 0) { for (i = 0; i < navigator.pluginslength; i++) { if (navigatorplugins[i].name.indexOf(plugin) >= 0) { f = navigator.plugins[i.descriptionsplit(pluginname)[1...
Provide a displayTickerAlert2 JS function. The following example returns a string for display by the caller:HTML Copy window.displayTickerAlert2 = (symbol, price) => { if (price < 20) { alert(`${symbol}: $${price}!`); return "User alerted in the browser."; } else { return "...
save(function(err) { if (err) done(err); else done(); }); }); }); }); Alternatively, just use the done() callback directly (which will handle an error argument, if it exists): describe('User', function() { describe('#save()', function() { it('should save without error'...
(new UpdateItemCommand(params)); const responseData = unmarshall(response.Attributes); console.log("Item updated successfully: ", responseData); return responseData; } catch (error) { if (error.name === "ConditionalCheckFailedException") { console.log("Condition check failed: I...
If the map service is requested from a different domain, a CORS enabled server or a proxy is required. Reference an ArcGIS portal Item ID You can also create a MapImageLayer from its ID if it exists as an item in ArcGIS Online or ArcGIS Enterprise. For example, the following snippet sho...
functionf() {console.log(bar);// undefinedvarbar ='abc';console.log(bar);// abc} 我们可以看到变量“bar”已经存在于“f()”的第一行,但它还没有值;也就是说,声明已经被提升,但赋值没有。JavaScript 执行f()时,就好像它的代码是: functionf() {varbar;console.log(bar);// undefinedbar ='ab...
layer).then((layerView) => { // Remove any previous highlight, if it exists hoverHighlight?.remove(); // Highlight the hit features with the temporary highlight options, which are pre-configured for this use case hoverHighlight = layerView.highlight(graphic, { name: "temporary" });...