Code blocks for *Optional (null-safe) in Javascript* Medium article

deep-default.js

const evaluation = obj && obj.prop1 && obj.prop1.prop2 && obj.prop1.prop2.prop3;

console.log( evaluation != null ? evaluation : "SomeDefaultValue" );

deep-undefined.js

console.log( obj && obj.prop1 && obj.prop1.prop2 && obj.prop1.prop2.prop3 );

lodash-get.js

var object = { 'a': [{ 'b': { 'c': 3 } }] };
 
_.get(object, 'a[0].b.c'); // => 3
 
_.get(object, ['a', '0', 'b', 'c']); // => 3
 
_.get(object, 'a.b.c', 'default'); // => 'default'

optional.cs

SomeClass obj;

obj?.prop1?.prop2?.prop3 ?? "SomeDefaultValue";

optional.java

SomeClass object;

Optional.ofNullable(object)
 .map(obj -> obj.prop1)
 .map(obj -> obj.prop2)
 .map(obj -> obj.prop3)
 .orElse("SomeDefaultValue");

optional.kt

val obj: SomeClass?

obj?.prop1?.prop2?.prop3 ?: "SomeDefaultValue";

print-undefined.js

let obj;

console.log(obj && obj.someProp); // Prints undefined

proxy-optional.js

function optional(obj, evalFunc, def) {
  
  const handler = {
   get: function(target, prop, receiver) {
     const res = Reflect.get(…arguments);
     return typeof res === "object" ? proxify(res) : res != null ? res : def;
   }
  };
 
  const proxify = target => {
    return new Proxy(target, handler);
  };

  return evalFunc(proxify(obj, handler));
  
}

const obj = {
  items: [{ hello: "Hello" }]
};
 
optional(obj, target => target.items[0].hello, "def")); // => Hello
optional(obj, target => target.items[0].hell, { a: 1 })); // => { a: 1 }

regex-optional.js

function optionalAccess(obj, path, def) {
  const propNames = path.replace(/\]|\)/, "").split(/\.|\[|\(/);

  return propNames.reduce((acc, prop) => acc[prop] || def, obj);
}

const obj = {
  items: [{ hello: "Hello" }]
};

optionalAccess(obj, "items[0].hello", "def"); // => Hello
optionalAccess(obj, "items[0].he", "def"); // => def