DOCTYPEhtml>//js对象varuser={name:"张学友",address:"中国香港"};console.log(typeof(user));console.log(typeof(null));console.log(typeof(undefined));console.log(user.name);console.log(user.age);if(user.age){console.log(user.age);}else{console.log("没有age属性");}//为false的情况vari...
// Two slashes start single-line commentsvarx;// declaring a variablex=3+y;// assigning a value to the variable `x`foo(x,y);// calling function `foo` with parameters `x` and `y`obj.bar(3);// calling method `bar` of object `obj`// A conditional statementif(x===0){// Is ...
Return Fields:* 点击查询(GET)按钮并滚动到屏幕底部。 查询实际上返回了来自数据库的所有字段的所有图层数据,但 ArcGIS Server 将结果限制为 1000 个要素。请注意浏览器的 URL 已更改。以下 URL 是用于触发此查询的 REST GET 请求 URL:sampleserver3.arcgisonline.com/ArcGIS/rest/services/BloomfieldHillsMichigan/...
因此,Number()转换为实际数字的许多值被parseFloat()转换为NaN: >parseFloat(true)// same as parseFloat('true')NaN>Number(true)1>parseFloat(null)// same as parseFloat('null')NaN>Number(null)0 parseFloat()将空字符串解析为NaN: >parseFloat('')NaN>Number('')0 parseFloat()解析到最后一个合法字符,...
it would be important that they both get the same object, even ifpriorThinggets assigned over and over so that both functions share the same lexical environment. But as soon as a variable is used by any closure, it ends up in the lexical environment shared by all closures in that scope....
If you declare a local variable inside a function with the exact same name as a global variable, then the local variable will hide the global variable. In the next example, the local client variable hides the global client variable. copy var client = "Joan"; // global function getClien...
Backticks are generally used when you need to insert variables or expressions into a string. This is done by wrapping variables or expressions with ${variable or expression}. For example, // strings example let name1 = 'Peter'; let name2 = "Jack"; let result = `The names are ${name...
To get started, let’s say we want to build a little browser for the people in our lives, as shown inFigure 2. Figure 2 Binding an Object to a Set of HTML Elements The idea is that we can have a number of people through whom we can navigate, each with a name, age and a favor...
Select the Console tab to see the console.log message, current class name: dark-theme. Using the console, you can get interesting insights from your JavaScript code. Add more console messages to understand which parts of your code are getting executed and to know the current values of other ...
// here we are in global scope var globalVariable = 'xyz'; function f() { var localVariable = true; function g() { var anotherLocalVariable = 123; // All variables of surround scopes are accessible localVariable = false; globalVariable = 'abc'; } } // here we are again in global...