how to check if a variable has value in javascript code example

Example 1: javascript check if not null

//Even if the value is 0, this will execute. 

if (myVar !== null) {...}

//If you don't want it to execute when it's 0, then set it as

if (myVar) {...}

//This will return false if var value is 0.

Example 2: How can I test whether a variable has a value in JavaScript?

if (typeof variable == "undefined") {...} --> return true if variable undefined

//An empty string evaluates to FALSE in JavaScript so you can just do:
if (variable) {...}

Example 3: javascript check if object is null or empty

if (typeof value !== 'undefined' && value) {
    //deal with value'
};

Example 4: javascript check if undefined or null or empty string

// simple check do the job
if (myString) {
 // comes here either myString is not null,
 // or myString is not undefined,
 // or myString is not '' (empty).
}

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Sql Example

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