Unverified60% confidenceFactExact time
在ES6之前，JavaScript只有var关键字用于变量声明
2
Sources
60%
Confidence
Medium-term (~90 days)
Relevance
7/2/2026
First Seen
Valid until: 9/30/2026
Sources
JavaScript Fundamentals: A Complete Guide to Variables, DOM Manipulation, Event Handling, and API Calls
bilibiliFireUG技术社区6/21/2026
Related Claims
Unverified对于var声明，JavaScript引擎会将声明提升但不提升赋值，因此在声明前访问变量会得到undefined而非报错57% similarUnverifiedTypeScript 编译器 tsc 会剥离类型标注生成标准 JavaScript，并可通过 tsconfig.json 的 target 字段进行语法降级（如将 ES2022 编译为 ES5）56% similarUnverifiedJavaScript中字符串与数字相加时会进行隐式类型转换，'5' + 3的结果是字符串'53'而非数字8。53% similarUnverifiedJavaScript的基本数据类型包括String、Number、Boolean、Array和Object51% similar
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