Will the ?. Operator (Optional Chaining) be supported one day?

Question

Some Scripting languages (e.g. TypeScript since recently, and as it seems also some JavaScript implementations) provide a new operator: "?."

It is a shortcut operator: The purpose is to access variables of an object, but first checking if the object or variable is actually defined. This would avoid a lot of extra if(undefined) checking in many medini scripts.

Assume for instance that you want to print the last name of the customer that is related with a certain order.

Traditionally you write something like

console.log(currentOrder.customer.lastName);

but the script breaks when there is no customer or the customer's last name is undefined. So you need to implement some extra checks by hand.

With the new operator it would be

console.log(currentOrder?.customer?.lastName);

The access is only executed if the object is defined.

Any chances to get a JavaScript Interpreter version into medini that can support this?

medini_1024169437 · Answer

Interesting. I meanwhile checke dthe linked feature map abive again and the entry is gone! So its not aymore mentione dthere, strange. If I would have not made a screenshot I would not believe that I saw it... :-(

Jan

medini_1063548292 · Answer

Bernard the only possible solution here is to use polyfill on Object prototype

I have define something similar to get safe results or even a last valid ( not undefined) values to shorted an simplify the coding

/**
 * Function to call a query on Object (Array, {}, Object.getValidOrSelf)
 * It will return the first defined value /function return , decreasing the query from right to left 
 * Any invalid or undefined results are silently ignored 
 * if all fails full , subqueries the return value is the object (obj)
 * Internally following query is formed 
 * 'return obj'+query+';'
 * Argument Object is mapped to 'obj' variable ( can be used in the query)
 *
 * @param {String} query : Optional ,correct query separated by commas, starting with dot or []. if target is Array 
 * @param {Object} obj : Optional, if not provided using the caller as an object
 * @returns last successful query result or caller object
 */
Object.prototype.getValidOrSelf = function (query, obj) {
 obj = obj == undefined ? this : obj;
 var res = obj;
 (query + "").split(".").forEach((k, id, keys) => {
 try {
 //console.log(keys.slice(0, keys.length - id).join("."));
 res = Function("obj", "return obj" + keys.slice(0, keys.length - id).join("."))(obj);
 }
 catch (e) {
 }
 if (!(res == undefined) && (res != obj)) {
 //console.log("breaking " + id + "{0}", res);
 keys.length = id + 1;
 }
 });
 return res;
}

/**
 * Function to return successful query result or undefined
 * Internally following query is formed 
 * 'return obj'+query+';'
 * Argument Object is mapped to 'obj' variable ( can be used in the query)
 * argument Object
 * 
 * @param {String} query : Optional ,correct query separated by commas, starting with dot or []. if target is Array 
 * @param {Object} obj : Optional, if not provided using the caller as anj object, 
 * @returns successful result or undefined
 */
Object.prototype.getsafe = function (query, obj) {
 obj = obj == undefined ? this : obj;
 var res = undefined;
 try {
 res = Function("obj", "return obj" + query)(this);
 }
 catch (e) {
 }
 return res;
}

Examples:

// Example 1:
 // variable x holding an EObject
 [].getValidOrSelf(".eAllStructuralFeatures.toArray().map(f=>f.name).undefinedAttribute",x);
 [x].getValidOrSelf("[0].eAllStructuralFeatures.toArray().map(f=>f.name).undefinedAttribute");
 Object.getValidOrSelf(".eAllStructuralFeatures.toArray().map(f=>f.name).undefinedAttribute",x);
 // returned is the last valid query :: map (...) an array with collected attribute names of structural attributes
 // Example 2:
 //variable is ann Object rootScope this or a simple javascript object {parent:value,parent2:{att1:1}};
 var x = {
 parent: function(value){return value},
 parent2: { att1: 1 },
 granny: 70
 };

var y = {
 granny: 20,
 grandpa:100
 };
 * returns x.parent function object
 x.getValidOrSelf(".parent")

// returns call x.parent function (result is 675)
 x.getValidOrSelf(".parent(675)")
 //returns [x]
 [x].getValidOrSelf()
 // returns y.granny
 x.getValidOrSelf(".granny.att1",y) 
// returns x.granny
 x.getValidOrSelf(".granny.att1")

// Example:
 [1].getSafe("[0]")
// => returns 1

x.getSafe(".parent2")
// => returns x.parent2

x.getSafe("[parent](1)") 
//=> returns parent function call (1)

x.getSafe("[parent]()")
// => returns parent function call (undefined)

x.getSafe("[parent]()==1?obj.parent():100")
// => returns 100 , obj is internally mapped to an argument Object

x.getSafe(".granny",y)
// => returns y.granny

Marian

medini_1024169437 · Answer

Just some additional notes on that subject: with Version 2024 R2 we updated the Rhino engine recently. The included version is now "Rhino 1.7.10 2018 04 09" which is quite a huge step forward, for example by supporting arrow functions.

Within a script it is easy to detect the engine and language version by using something like:

console.log(Packages.org.mozilla.javascript.Context.currentContext.implementationVersion);
console.log(Packages.org.mozilla.javascript.Context.currentContext.languageVersion);

Happy Detection

Jan