When you code, and you have to write an if statement like lines below:
if (x_value){
//some code here
}
what do you think is logically correct value of the x_value? Either true or false, right?
In Javascript though, you'll see some condition where true and false is not used in a boolean context but something else. Look at this code for example:
let name='Alex';
if(name){
console.log("Hi ",name);
}
in the line you see conditional statement if(name). While it requires boolean expression, name provided there is not a boolean value. It is a string, yet it is a valid expression. Why?
Because implicitly, Javascript do a type coercion, an implicit type conversion, so the string 'Alex' will be converted to boolean value, true.
An expression that will get type coercion to a true value is considered a Truthy value, while expression which will get type coercion to a false value is considered a Falsy value.
Bellow are some expression that Javascript consider as Truthy value when it comes to a boolean context:
//a non empty string
if ('false'){// 'false' is not an empty string, it has content 'false'
//code here will be executed
}
//an object either with or without properties
if ({} /* or {value: 0} */){// object with no property
//code here will be executed
}
//an array either empty or has some values
if ([] /* or [1,2,3] */){// array with no or some items
//code here will be executed
}
//a number other than 0
if (-1 /* or 5 or 0.2 or -100 or Infinity or -Infinity */){// non zero number
//code here will be executed
}```
In contrast to Truthy values, here are some sample expressions of Falsy value:
`if ("")//empty string
if (null)//null value
if (0 /* or -0 */) //zero number
if (undefined)//undefined value
if (0n)
if (NaN)
`
In practice you'll find yourself love the usage of Truthy and Falsy value because you can shorten your code and made them more clean as well. You'll also find this used a lot in people's code, so understand this concept will definitely help you grow better as a software developer.
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