Stringify ( ) - Optional Parameters

    // Lesser known features when using JSON.stringify( )
    
    let obj = {name: "Walter",
        last: "Sobchack",
        age: 50, 
        angry: true, 
        betscore: 200, 
        armed: true};
    let log = console.log; 
    let str;
    
    str = JSON.stringify(obj);
    log('1', str);
    
    // USING AN ARRAY TO FILTER THE OBJECT
    str = JSON.stringify(obj, ['age', 'angry', 'last']);	// allows you to specify what you want from the object 
    log('\n2', str);
    
    // USING A FUNCTION TO FILTER
    function replace(key, val)	{
        if (typeof val === 'string'){
            return undefined;
        } else {
            return val;
        }
    } 
    str = JSON.stringify(obj, replace);
    log('\n3', str);	// will return all properties except those with a string value
    
    // PLACING CHARACTERS BEFORE PROPERTIES
    str = JSON.stringify(obj, null, 4);	// returns object with 4 spaces before each property
    log('\n4', str);