alert(a); // undefined alert(b); // Can't find variable: b b = 10; var a = 20; 3.2. 三种函数类型 1)函数声明在程序级别或另一函数的函数体: function foo() { // ... } function globalFD() { function innerFD() {} } 2)函数表达式在表达式的位置: var foo = function () { //...
AI代码解释 VariableDeclaration:not(ExportNamedDeclaration>.declaration)>VariableDeclarator.declarations:matches([init.type="ArrayExpression"],:matches([init.type="CallExpression"],[init.type="NewExpression"])[init.optional!=true][init.callee.type="Identifier"][init.callee.name="Array"],[init.type="...
// 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 ...
Especially in the case of values returned by the REST API response of the server, we may need to know the type of the value or variable before we further code to process it. Using the typeof Operator to Find the Type of Variable typeof is a unary operator in javascript that returns ...
// 用于找出第一个符合条件的数组成员,如果没有找到返回undefined var ary = [{ id: 1, name: '张三' }, { id: 2, name: '李四' }]; let target = ary.find(item => item.id == 2); console.log(target) let target1 = ary.find(item => item.id == 3); console.log(target1) 1...
解析时,会生成 scope_get_var 和 scope_put_var,在执行 resolve_variable 函数时会将解析后的指令转换成局部变量 get_loc 和 put_loc,自由变量 get_var_ref 和 put_var_ref。获取局部和外层变量使用的是 get_closure_var 函数,get_closure_var 函数会将当前函数所要用的变量记录在函数定义对象 JSFunctionDef...
The typeof Operator You can use the JavaScripttypeofoperator to find the type of a JavaScript variable. Thetypeofoperator returns the type of a variable or an expression: Example typeof""// Returns "string" typeof"John"// Returns "string" ...
functionisArray(variable){returnArray.isArray(variable);} 04、展平嵌套数组的数组: functionflattenArray(array){returnarray.flat();} 05、生成介于最小值和最大值之间的随机数: functiongetRandomNumber(min, max){returnMath.floor(Math.random() * (max...
varmap;//Global variablerequire(["esri/map"],function(Map) { map =newMap("myMap", {basemap:"national-geographic"}); }); }); 这意味着我们可以在浏览器控制台中访问地图的属性。在缩放地图和所需的范围作为地图初始范围之后,使用Ctrl+Shift+I命令(在 Chrome 中)打开开发者工具。在 JavaScript ...
Theletkeyword allows you to declare a variable with block scope. Example varx =10; // Here x is 10 { letx =2; // Here x is 2 } // Here x is 10 Try it Yourself » Read more aboutletin the chapter:JavaScript Let. JavaScript const ...