Get First Non-Null or Undefined Argument in JavaScript



In JavaScript, there are often times when we need to find the first non-null/undefined argument in a function. This can be a tricky task, but luckily there are a few methods that can help us accomplish this

Using Array.prototype.find()

One method that can be used to get the first non-null/undefined argument in JavaScript is the Array.prototype.find() method. This method returns the value of the first element in an array that passes a given test. In our case, we can use this method to find the first non-null/undefined argument by passing a test that checks if the argument is not null/undefined.

Example

In the example below, we define a function to find the first non-null or undefined argument.

Open Compiler
<html> <head> <title>Example: finding first non-null arguements</title> </head> <body> <h2> Array.prototype.find() Method</h2> <div id="arguments"></div> <div id="result"></div> <script> function findFirstNonNullArgument(...args) { return args.find(arg => arg != null); } var result = findFirstNonNullArgument(null, undefined, "Hello", "World"); document.getElementById("arguments").innerHTML = `Arguments: null, undefined, "Hello", "World"`; document.getElementById("result").innerHTML = "<br>First Non-Null Argument: " + result; </script> </body> </html>

As we can see from the code above, the findFirstNonNullArgument() function takes in a variable number of arguments and uses the find() method to return the first non-null/undefined argument.

Using Array.prototype.filter()

Another method that can be used to get the first non-null/undefined argument in JavaScript is the Array.prototype.filter() method. This method creates a new array with all elements that pass the given test. In our case, we can use this method to find the first non-null/undefined argument by passing in a test that checks if the argument is not null/undefined.

Example

Below is the full working code.

Open Compiler
<html> <head> <title>Example: finding first non-null arguements</title> </head> <body> <h2> Array.prototype.filter() Method</h2> <div id="arguments"></div> <div id="result"></div> <script> function findFirstNonNullArgument(...args) { return args.filter(arg => arg != null)[0]; } document.getElementById("arguments").innerHTML = `Arguments: null, undefined, "Hello", "World"`; document.getElementById("result").innerHTML = "<br>First non-nul argument: " + findFirstNonNullArgument(null, undefined, "Hello", "World") </script> </body> </html>

As we can see from the code above, the findFirstNonNullArgument() function takes in a variable number of arguments and uses the filter() method to return the first non-null/undefined argument.

Using a for loop

Another method that can be used to get the first non-null/undefined argument in JavaScript is by using a for loop. This method loops through all of the arguments and checks if each argument is not null/undefined. If it finds an argument that is not null/undefined, it returns that argument.

Example

Below is the full working code

Open Compiler
<html> <head> <title>Examples</title> </head> <body> <div id="result"></div> <script> function findFirstNonNullArgument(...args) { for (let arg of args) { if (arg != null) { return arg; } } } document.getElementById("result").innerHTML = findFirstNonNullArgument(null, undefined, "Hello", "World") </script> </body> </html>

As we can see from the code above, the findFirstNonNullArgument() function takes in a variable number of arguments and uses a for loop to return the first non-null/undefined argument.

Conclusion

In this article, we looked at three different methods that can be used to get the first non-null/undefined argument in JavaScript. Each method has its own advantages and disadvantages, so it is important to choose the right method for the task at hand.

Updated on: 2022-07-01T12:37:05+05:30

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