Truthy and Falsy
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<title>Truthy and Falsy </title>
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<!--
All JavaScript values have an inherent truthyness or falsyness about them.
Falsy values listed below, rest all are truthy:
- false
- null
- "" (empty string)
- 0
- undefined
- NaN
-->
<h1>Demo: Truthy and Falsy values</h1>
<div>
<h2>When the string is empty, it has falsy value</h2>
<p id="para1"></p>
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<div>
<h2>When the variable is undefined, it has falsy value</h2>
<p id="para2"></p>
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<h2>0 (zero) will be false, hence '!0' is 1 i.e true value</h2>
<p id="para3"></p>
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<!-- JavaScript code Starts here -->
<script>
/************************************************/
// Truthy & Falsy Values
// Example : When the string is empty, then it has falsy value
//
let cityName = ""; // cityName is empty string
if (cityName) { // if condition will be false because cityName is empty string
document.getElementById('para1').innerHTML =
`City name is ${cityName}`;
} else
document.getElementById('para1').innerHTML =
`City name is BLANK`;
/************************************************/
// Truthy & Falsy Values
// Example : undefined variable will be false, hence it has falsy value
//
let isVaccinated; // isVaccinated is undefined
if (isVaccinated) { // if condition will be false because isVaccinated is undefined
document.getElementById('para2').innerHTML =
"He/She is VACCINATED";
} else
document.getElementById('para2').innerHTML =
"He/She is NOT VACCINATED";
/************************************************/
// Truthy & Falsy Values
// Example : 0 (zero) will be false, hence '!0' is 1 i.e true value
//
let favNum = 0; // favNum contains 0
if (!favNum) { // if condition will be true because '!0' is 1, which is true
document.getElementById('para3').innerHTML =
"Favorite number cannot be 0 (zero).";
}
</script>
<!-- JavaScript code Ends here -->
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