javascript/typescript 对象空检查

Question

以以下两种方式进行空检查时，性能是否存在差异 -

if (!someObject) {
   // dosomething
}

对比

if (someObject != null) {
   // dosomething
}

Answer 1

!someObject 检查所有虚假值。

Not ( empty string, undefined, null, 0, false) - will all pass the condition

第一个条件只检查 null。

 if (someObject !== null) {
    console.log('falsey');
 }

 someObject = null;      // no message in console
 someObject = '';        // falsey
 someObject = undefined; // falsey
 someObject = 0;         // falsey
 someObject = false;     // falsey

虚假检查

if (!someObject) {
    console.log('falsey');
 }

 someObject = null;      // no message in console
 someObject = '';        // no message in console
 someObject = undefined; // no message in console
 someObject = 0;         // no message in console
 someObject = false;     // no message in console