Object-Oriented JavaScript - Third Edition

Default parameters

Function parameters can be assigned default values. While calling the function, if a parameter is omitted, the default value assigned to the parameter is used:

    function render(fog_level=0, spark_level=100){ 
      console.log(`Fog Level: ${fog_level} and spark_level:
       ${spark_level}`) 
    } 
    render(10); //Fog Level: 10 and spark_level: 100 

In this example, we are omitting the spark_level parameter, and hence the default value assigned to the parameter is used. It is important to note that undefined is considered as an absence of parameter value; consider the following line of code, for example:

    render(undefined,10); //Fog Level: 0 and spark_level: 10 

While providing default values of parameters, it is possible to refer to other parameters ...