这种非标准的方式已经在40的版本之后被移除了. 现在开始它会在控制台里抛出一个SyntaxError("for-in loop head declarations may not have initializers") 警告。(bug 748550以及bug 1164741)。 像其他引擎 V8(Chrome),Chakra (IE/Edge), JSC (WebKit/Safari) 正在研究去除这种不标准的行为。
1console.log('toString'in{});//true 这里的toString方法,是Object.prototype的一个方法。 参考资料: 1.MDN文档 2.Javascript学习笔记-详解in运算符 3.[翻译]JavaScript秘密花园 - Array, Array Constructor, for in loop, typeof, instanceOf(更详细地内容请点这里)...
属性arrCustom和objCustom没有被打印,因为它们是继承属性。 for...of循环迭代并打印iterable按照数组(数组是可迭代的)定义要进行迭代的值。对象的元素3、5、7被打印,但对象的属性没有被打印。 Specification ECMAScript® 2026 Language Specification #sec-for-in-and-for-of-statements...
However it can be iterated over in a standard for loop over its indices, or converted to an Array. Note: Typically list interfaces like StyleSheetList wrap around Array types, so you can use Array methods on them. This is not the case here for historical reasons. However, you can convert...
Initializers in var declarations of for...in loops headers are deprecated and produce syntax errors in strict mode. The initializer expression is evaluated and assigned to the variable, but the value would be immediately reassigned on the first iteration of the loop. Normally, the catch block of...
For future-facing usages, consider using for..of loops and the iterator protocol. The StopIteration object is used to tell the end of the iteration in the legacy iterator protocol. Syntax StopIteration Description StopIteration is a part of legacy iterator protocol, and it will be removed at ...
你可以在 GitHub 上找到本章中提到的代码文件,网址为github.com/PacktPublishing/Modern-CMake-for-Cpp-2E/tree/main/examples/ch12。 要构建本书中提供的示例,请始终使用以下推荐的命令: cmake -B <build tree> -S cmake --build <build tree> 确保将占位符<...
<%. The for loop in JS can begin with one <% %> block, transition to output mode, and finish up in a second <% %> JS block. For more details on EJS syntax, check out the upstream module documentation. Tips You can see a list of macros and how they are used on MDN on the ...
If the function or object is already in the list of event listeners for this target, the function or object is not added a second time. Note: If a particular anonymous function is in the list of event listeners registered for a certain target, and then later in the code, an identical ...
Becausefibonacci()is an infinite iterator, you can't use aforloop to iterate it directly. You absolutely can, provided that you eventually break out of the loop through some means such asbreak,return,throw, etc. What did you expect to see?