javascript - What does the ! (exclamation mark) mean before selector in jQuery -

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इस सवाल का पहले से ही एक उत्तर है: < / P>

  • 2 जवाब

मुझे पहले से ही पता है कि < कोड>! को सामान्यत: "code" नहीं , नहीं , और null में जावास्क्रिप्ट में अभिव्यक्त करने के लिए उपयोग किया जाता है।

लेकिन jQuery के चयनकर्ता से पहले उद्गार चिल्लाना क्या मतलब है? 

  यदि (! $ ('चयनकर्ता')। हैक्सेल ('कुछ')) {कुछ करो}  < 
 
 
 
 
 
 
 यह एक बूलीयन को अस्वीकार करता है। 
 
 अर्थ: 
 
 
 
 
 और 
 
 
 गलत हो जाता है 
 
 
 
 इस उदाहरण में इसका मतलब है: 
 <पूर्व>  यदि (! $ ('चयनकर्ता')। हैक्लास ('कोई चीज़    हैक्लासेल  फ़ंक्शन के परिणाम पर। ऐसा है जैसे आपने ब्रैकेट्स का उपयोग किया है (लेकिन आपको ब्रैकेट्स का उपयोग नहीं करना है, जावास्क्रिप्ट जानता है कि इसका मतलब है)। 
 
 ! ($ ('Selector')। हैक्लास ('कुछ' ) / * उदाहरण के लिए रिटर्न सही * /) / * अब यह झूठी है * /

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