Javascript

<div dir="ltr" style="text-align: left;" trbidi="on">
<div class="MsoNormal">
<span style="background: white; color: #242729;">You can just check if the <em><span style="border: none 1.0pt; font-family: "calibri" , sans-serif; padding: 0in;">variable</span></em> has a </span><code><span style="background: #eff0f1; border: none 1.0pt; color: #242729; font-size: 10.0pt; padding: 0in;">truthy</span></code><span style="background: white; color: #242729;"> value or not. That means<o:p></o:p></span></div>
<div class="MsoNormal">
<span style="background: white; color: #242729;">if( value ) {<o:p></o:p></span></div>
<div class="MsoNormal">
<span style="background: white; color: #242729;">}<o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<b><span style="background: white; color: #242729;">will evaluate to true</span></b><span style="background: white; color: #242729;"> if value is not:<o:p></o:p></span></div>
<ul style="margin-top: 0in;" type="disc">
<li class="MsoNormal" style="color: #242729; margin-left: 0in; mso-list: l0 level1 lfo1; tab-stops: list .5in;"><span style="background: white; mso-fareast-font-family: "Times New Roman";">null<o:p></o:p></span></li>
<li class="MsoNormal" style="color: #242729; margin-left: 0in; mso-list: l0 level1 lfo1; tab-stops: list .5in;"><span style="background: white; mso-fareast-font-family: "Times New Roman";">undefined<o:p></o:p></span></li>
<li class="MsoNormal" style="color: #242729; margin-left: 0in; mso-list: l0 level1 lfo1; tab-stops: list .5in;"><span style="background: white; mso-fareast-font-family: "Times New Roman";">NaN<o:p></o:p></span></li>
<li class="MsoNormal" style="color: #242729; margin-left: 0in; mso-list: l0 level1 lfo1; tab-stops: list .5in;"><span style="background: white; mso-fareast-font-family: "Times New Roman";">empty string ("")<o:p></o:p></span></li>
<li class="MsoNormal" style="color: #242729; margin-left: 0in; mso-list: l0 level1 lfo1; tab-stops: list .5in;"><span style="background: white; mso-fareast-font-family: "Times New Roman";">0<o:p></o:p></span></li>
<li class="MsoNormal" style="color: #242729; margin-left: 0in; mso-list: l0 level1 lfo1; tab-stops: list .5in;"><span style="background: white; mso-fareast-font-family: "Times New Roman";">false<o:p></o:p></span></li>
</ul>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
TO be more safe , we can use as below which takes care of not declared variable as well <o:p></o:p></div>
<div class="MsoNormal">
if (typeof value != 'undefined' && value) {<o:p></o:p></div>
<div class="MsoNormal">
    //deal with value'<o:p></o:p></div>
<br />
<div class="MsoNormal">
};<o:p></o:p></div>
</div>

Javascript truthy check

You can just check if the variable has a truthy value or not. That means if( value ) { } will evaluate to true if value is no...

+ Read more »