I'm trying to validate a JSON object with node.js. Basically, if condition A is present then I want to make sure that a particular value is in an array which may not be present. I do this in python using dictionary.get because that will return a default value if I look up something that isn't present. This is what it looks like in python
if output.get('conditionA') and not 'conditionB' in output.get('deeply', {}).get('nested', {}).get('array', []):
print "There is an error somewhere you need to be fixing."
I'd like to find a similar technique for javascript. I tried using defaults in underscore to create the keys if they aren't there but I don't think I did it right or I'm not using it the way it was intended.
var temp = _.defaults(output, {'deeply': {'nested': {'array': []}}});
if (temp.hasOwnProperty('conditionA') && temp.deeply.nested.array.indexOf('conditionB') == -1) {
console.log("There is an error somewhere you need to be fixing.");
}
It seems like if it runs into an output where one of the nested objects is missing it doesn't replace it with a default value and instead blows with a TypeError: Cannot read property 'variety' of undefined where 'variety' is the name of the array I'm looking at.
Or better yet, here's a quick wrapper that imitates the functionality of the python dictionary.
http://jsfiddle.net/xg6xb87m/4/
function pydict (item) {
if(!(this instanceof pydict)) {
return new pydict(item);
}
var self = this;
self._item = item;
self.get = function(name, def) {
var val = self._item[name];
return new pydict(val === undefined || val === null ? def : val);
};
self.value = function() {
return self._item;
};
return self;
};
// now use it by wrapping your js object
var output = {deeply: { nested: { array: [] } } };
var array = pydict(output).get('deeply', {}).get('nested', {}).get('array', []).value();
Edit
Also, here's a quick and dirty way to do the nested / multiple conditionals:
var output = {deeply: {nested: {array: ['conditionB']}}};
var val = output["deeply"]
if(val && (val = val["nested"]) && (val = val["array"]) && (val.indexOf("conditionB") >= 0)) {
...
}
Edit 2 updated the code based on Bergi's observations.
The standard technique for this in JS is (since your expected objects are all truthy) to use the || operator for default values:
if (output.conditionA && (((output.deeply || {}).nested || {}).array || []).indexOf('conditionB') == -1) {
console.log("There is an error somewhere you need to be fixing.")
}
The problem with your use of _.defaults is that it's not recursive - it doesn't work on deeply nested objects.
If you'd like something that's a little easier to use and understand, try something like this. Season to taste.
function getStructValue( object, propertyExpression, defaultValue ) {
var temp = object;
var propertyList = propertyExpression.split(".");
var isMatch = false;
for( var i=0; i<propertyList.length; ++i ) {
var value = temp[ propertyList[i] ];
if( value ) {
temp = value;
isMatch = true;
}
else {
isMatch = false;
}
}
if( isMatch ) {
return temp;
}
else {
return defaultValue;
}
}
Here's some tests:
var testData = {
apples : {
red: 3,
green: 9,
blue: {
error: "there are no blue apples"
}
}
};
console.log( getStructValue( testData, "apples.red", "No results" ) );
console.log( getStructValue( testData, "apples.blue.error", "No results" ) );
console.log( getStructValue( testData, "apples.blue.error.fail", "No results" ) );
console.log( getStructValue( testData, "apples.blue.moon", "No results" ) );
console.log( getStructValue( testData, "orange.you.glad", "No results" ) );
And the output from the tests:
$ node getStructValue.js
3
there are no blue apples
No results
No results
No results
$
You can check that a key exists easily in javascript by accessing it.
if (output["conditionA"]) {
if(output["deeply"]) {
if(output["deeply"]["nested"]) {
if(output["deeply"]["nested"]["array"]) {
if(output["deeply"]["nested"]["array"].indexOf("conditionB") !== -1) {
return;
}
}
}
}
}
console.error("There is an error somewhere you need to be fixing.");
return;
Related
I have code that requires multiple If Else statements but I'm not sure how to format it so that each runs:
let example = first;
let example2 = second;
let example3 = third;
if (example === something) {
return null;
} else {
return something;
}
if (example2 === somethingElse) {
return null;
} else {
return somethingElse;
}
if (example3 === somethingMore) {
return null;
} else {
return somethingMore;
}
But this doesn't work because of the multiple else statements, I was wondering if there was a way to do this? I also tried to put the data into an array or objects to iterate through but that won't work either.
Please help! :)
return will immediate return from first if, so store all result in object or array and return it as below
let example = 'first';
let example2 = 'second';
let example3 = 'third';
var return_data = {};
if (example === 'something') {
return_data.example = null;
} else {
return_data.example = something;
}
if (example2 === 'somethingElse') {
return_data.example2 = null;
} else {
return_data.example2 = 'somethingElse';
}
if (example3 === 'somethingMore') {
return_data.example3 = null;
} else {
return_data.example3 = 'somethingMore';
}
return return_data;
You have to remove the return in the if / else blocks - using return will immediately exit the function wherever it's encountered. The way your code is now, you are basically short-circuiting the function (which is not what you're trying to do):
It would probably make more sense to restructure your code to use a variable like this:
//Add a variable to keep store your desired output if you want to flow thru all if/else blocks
function getVal(example) {
let val;
if (example === 'something1') {
val = 'a'
} else {
val = 'b';
}
return val;
}
console.log(getVal('something1'));
console.log(getVal('lorem'));
I'm not completely clear on what you are asking, but I think you want to be using "else if" statements: https://ncoughlin.com/javascript-notes-conditional-statements-loops/#If_Else_If_Else
let example = first;
let example2 = second;
let example3 = third;
if (example === something) {
return a;
} else if (example2 === somethingElse){
return b;
} else if (example3 === anotherThing){
return c;
} else {
return null;
}
You can do something like this :
myArray = [];
let example = first;
let example2 = second;
let example3 = third;
if (example === something) {
myArray.push(null);
} else {
myArray.(something);
}
if (example2 === somethingElse) {
myArray.push(null);
} else {
myArray.(somethingElse);
}
if (example3 === somethingMore) {
myArray.push(null);
} else {
myArray.(somethingMore);
}
return myArray;
Like Tom O. said return will immediatly exit your function. You can use something other than an array but remember return is executed only once.
Regardless of your approach, it seems like you want to build a "collection" of some sort (array, object, set, map, etc) then return it at the end.
But, the way you code it depends on the reason your function exists. Let's look at an example...
if (first === undefined) {
return null
} else {
return first
}
...This logic exists solely to ensure a "default" value is used for first - something like the null object pattern. For this use case, I might propose nullish coalescing to keep it simple (or something that could be easily replaced with it in the future):
first ?? null
// or, if you don't use babel/some kind of transpiler, you could want:
first !== undefined && first !== null ? first : null
// and since our default is null anyway, we can shorten this to:
first !== undefined ? first : null
Looking solely at your example, it seems like you could simply want to get default values like this for multiple variables. For that use case, you (or someone else coming across this question) might want a function similar to one in the code snippets below. Using objects and/or arrays for this can be handy because they can also be easily broken back out into multiple variables, if you wanted.
First, example functions using arrays:
// If you want default values for items in an array (static, all same default value)
const buildArrayWithDefault = (vals, defaultVal = null) => vals.map(
v => v !== undefined ? v : defaultVal // could be v ?? defaultVal
)
// If you want default values for items in an array (static, but defaults could all be different)
const buildArrayWithDefaults = (vals, defaultVals) => vals.map(
(v, idx) => v !== undefined ? v : defaultVals[idx] // could be v ?? defaultVals[idx]
)
// If you want default values for items in an array (dynamic via callback)
const buildArrayWithDefaults2 = (vals, getDefaultValue) => vals.map(
(v, idx) => v !== undefined ? v : getDefaultValue(v, idx)
)
// All of these return [ 1, 5, 3 ]
console.log(
buildArrayWithDefault([1, undefined, 3], 5),
buildArrayWithDefaults([1, undefined, 3], [ 4, 5, 6 ]),
buildArrayWithDefaults2([1, undefined, 3], (v, idx) => idx + 4)
)
Next, examples using objects:
// Hard-coded default values for an object (ternary)
const buildObject = (first, second, third) => ({
first: first !== undefined ? first : null, // or first ?? null
second: second !== undefined ? second : null,
third: third !== undefined ? third : null,
})
// Hard-coded default values for an object (default parameters)
const buildObject2 = (
first = null,
second = null,
third = null
) => (
{ first, second, third }
)
// ...or you can just use Object.assign()
const assignDefaults = (obj) => Object.assign(
{ first: null, second: null, third: null }, // defaults
obj
)
// Finally, allowing the function user to define their own defaults
// (At this point, you may just want to use Object.assign() directly)
const assignDefaults2 = (...args) => Object.assign({}, ...args.reverse())
// All of these should return { first: 1, second: null, third: null }
console.log(
buildObject(1),
buildObject2(1),
assignDefaults({ first: 1 }),
assignDefaults2({ first: 1 }, { first: null, second: null, third: null })
)
I'm trying to figure out how to check if a deeply nested JSON object, with several unknown arrays and properties contains a property that I'm looking for. I'm looking for a property that is called "isInvalid". If the field is there and the value of that key is true. I want to return false.
var checkValidity = function (data) {
for (var property in data) {
if (data.hasOwnProperty(property)) {
if (property == "isInvalid" && data[property] === true) {
return false;
}
else {
if (typeof data[property] === "object" && data[property] !== null) {
this.checkValidity(data[property]);
}
}
}
}
};
This is the code I've been trying out but I'm unable to get that to work. I have been looking into underscore also, but cant find the needed functions. Anyone has an idea? (No reg exp please)
If you really just want to check for property presence regardless of its particular location within JSON, then the easiest/fastest way is substring search in the source JSON string. If the latter is well-formed, then the property should be encoded in JSON as '"isInvalid":true'.
var checkValidity = function (jsonstr) {
return jsonstr.indexOf('"isInvalid":true') >= 0;
}
You can check like this
var s = {a:'1',b:'2'};
if(Object.getOwnPropertyNames(s).indexOf('a') != -1){
console.log('available');
}else{
console.log('Not available');
};
editing answer... UPDATE
var s = {
a1: '1',
b: '2',
c: {
a: '11'
}
};
var checkValidity = function (data) {
if (Object.getOwnPropertyNames(data).indexOf('a') != - 1) {
console.log('Found that key!!!');
} else {
for (var property in data) {
if (Object.getOwnPropertyNames(property).indexOf('a') != - 1) {
console.log('Found that key!!!');
} else {
if (typeof data[property] === 'object' && data[property] !== null) {
console.log('not found continue in inner obj..');
this.checkValidity(data[property]);
}
}
}
};
};
checkValidity(s);
It tests for every nesting level the property isInvalid and if not, all other properties as object and their content. Array#every breaks if one return is false.
function checkValidity(data) {
return !data.isInvalid && Object.keys(data).every(function (property) {
if (typeof data[property] === "object" && data[property] !== null) {
return checkValidity(data[property]);
}
return true;
});
}
var data = {
a: 1,
b: 2,
c: {
isInvalid: true,
a: false
}
};
document.write('checkValidity() should be false: ' + checkValidity(data) + '<br>');
data.c.isInvalid = false;
document.write('checkValidity() should be true: ' + checkValidity(data));
For complex json searching like this, I would use jsonpath ( http://goessner.net/articles/JsonPath/ ) which is the JSON equivalent of xpath.
To find the isInvalid field no matter where it is in the json, you would use it like this:
jsonPath(data, "$..isInvalid")
I was trying to write a generic clone function which should be able to do true deep cloning. I have come across this link, How to Deep clone in javascript and took the function from there.
That code workds pretty well when I try using direct Javascript. I did minor modifications in the code and tried to put in the JSNI code in GWT.
clone function:
deepCopy = function(item)
{
if (!item) {
return item;
} // null, undefined values check
var types = [ Number, String, Boolean ], result;
// normalizing primitives if someone did new String('aaa'), or new Number('444');
types.forEach(function(type) {
if (item instanceof type) {
result = type(item);
}
});
if (typeof result == "undefined") {
alert(Object.prototype.toString.call(item));
alert(item);
alert(typeof item);
if (Object.prototype.toString.call(item) === "[object GWTJavaObject]") {
alert('1st');
result = [];
alert('2nd');
item.forEach(function(child, index, array) {//exception thrown here
alert('inside for each');
result[index] = deepCopy(child);
});
} else if (typeof item == "GWTJavaObject") {
alert('3rd');
if (item.nodeType && typeof item.cloneNode == "function") {
var result = item.cloneNode(true);
} else if (!item.prototype) {
result = {};
for ( var i in item) {
result[i] = deepCopy(item[i]);
}
} else {
if (false && item.constructor) {
result = new item.constructor();
} else {
result = item;
}
}
} else {
alert('4th');
result = item;
}
}
return result;
}
And the list am passing to this function is like this:
List<Integer> list = new ArrayList<Integer>();
list.add( new Integer( 100 ) );
list.add( new Integer( 200 ) );
list.add( new Integer( 300 ) );
List<Integer> newList = ( List<Integer> ) new Attempt().clone( list );
Integer temp = new Integer( 500 );
list.add( temp );
if ( newList.contains( temp ) )
Window.alert( "fail" );
else
Window.alert( "success" );
But when I execute this, I get null pointer exception in the clone function immediately after alert("2nd") line.
Kindly help.
P.S: I am trying to get a generic clone method here that can be used to clone any object.
GWT prototyped objects don't have a forEach method; they do not inherit standard javascript object prototypes, as they are supposed to act like java objects, not javascript objects.
You could probably get away with Object.prototype.forEach.call(item, function(){})
Sorry for the title but I don't know how to explain it.
The function takes an URI, eg: /foo/bar/1293. The object will, in case it exists, be stored in an object looking like {foo: { bar: { 1293: 'content...' }}}. The function iterates through the directories in the URI and checks that the path isn't undefined and meanwhile builds up a string with the code that later on gets called using eval(). The string containing the code will look something like delete memory["foo"]["bar"]["1293"]
Is there any other way I can accomplish this? Maybe store the saved content in something other than
an ordinary object?
remove : function(uri) {
if(uri == '/') {
this.flush();
return true;
}
else {
var parts = trimSlashes(uri).split('/'),
memRef = memory,
found = true,
evalCode = 'delete memory';
parts.forEach(function(dir, i) {
if( memRef[dir] !== undefined ) {
memRef = memRef[dir];
evalCode += '["'+dir+'"]';
}
else {
found = false;
return false;
}
if(i == (parts.length - 1)) {
try {
eval( evalCode );
} catch(e) {
console.log(e);
found = false;
}
}
});
return found;
}
}
No need for eval here. Just drill down like you are and delete the property at the end:
parts.forEach(function(dir, i) {
if( memRef[dir] !== undefined ) {
if(i == (parts.length - 1)) {
// delete it on the last iteration
delete memRef[dir];
} else {
// drill down
memRef = memRef[dir];
}
} else {
found = false;
return false;
}
});
You just need a helper function which takes a Array and a object and does:
function delete_helper(obj, path) {
for(var i = 0, l=path.length-1; i<l; i++) {
obj = obj[path[i]];
}
delete obj[path.length-1];
}
and instead of building up a code string, append the names to a Array and then call this instead of the eval. This code assumes that the checks to whether the path exists have already been done as they would be in that usage.
//window["Fluent"]["Include"]
function setGlobalVariableByName(name,value)
{
var indexes = name.split(".");
var variable = null;
$.each(indexes, function()
{
if (variable == null){
variable = window[this];
}else{
variable = variable[this];
}
});
variable = value;
}
setGlobalVariableByName("Fluent.Include.JqueryPulse",true);
console.log(Fluent.Include.JqueryPulse) // prints false
this doesn't work, obviously. It would work if I just wanted to get the variable's value, but not for setting it.
window["Fluent"]["Include"]["JqueryPulse"] = true;
console.log(Fluent.Include.JqueryPulse) // prints true
how could I achieve something like this without using eval?
I'd need some way to programmatically add array indices to this, I'd guess
The following works, can you suggest a better way to code it in order to make it more DRY?
function setGlobalVariableByName(name,value)
{
var indices = name.split(".");
var parent;
$.each(indices, function(i)
{
if(i==indices.length-1){
if (!parent){
window[this] = value;
}else{
parent[this] = value;
}
}else if (!parent){
parent = window[this];
}else{
parent = variable[this];
}
});
}
setGlobalVariableByName : function(name, value)
{
var indices = name.split(".");
var last = indices.pop();
var parent;
$.each(indices, function(i)
{
if (!parent){
parent = window[this];
}else{
parent = variable[this];
}
});
if (!parent){
window[last] = value;
}else{
parent[last] = value;
}
}
You need to call
variable[this] = value
somehow. So you need to break the loop of the splited string before reching the last name, and then assign the value.
Ultimatively you need to call:
variable = window['Fluent']['Include']; // build this in a loop
variable['JqueryPulse'] = someValue; // then call this
Ultimately you're just building an object chain and setting the final item in the chain to a value. Also, I would add a check to ensure that items which are already objects do not get overwritten so that their existing properties don't get lost:
//bootstrap the object for demonstration purposes--not necessary to make code work
window.Fluent = {
Include: {
foo: 'bar', //don't want to lose this'
JqueryPulse: false //want to set this to true
}
};
//define function
function setGlobalItemByName( name, value )
{
var names,
finalName,
//no need to figure out if this should be assigned in the loop--assign it now
currentOp = window;
if( typeof name === 'string' && name !== '' )
{
names = name.split( '.' );
//no need to track where we are in the looping--just pull the last off and use it after
finalName = names.pop();
$.each( names, function()
{
//If the current item is not an object, make it so. If it is, just leave it alone and use it
if( typeof currentOp[this] !== 'object' || currentOp[this] === null )
{
currentOp[this] = {};
}
//move the reference for the next iteration
currentOp = currentOp[this];
} );
//object chain build complete, assign final value
currentOp[finalName] = value;
}
}
//use function
setGlobalItemByName( 'Fluent.Include.JqueryPulse', true );
//Check that Fluent.Include.foo did not get lost
console.log( Fluent.Include.foo );
//Check that Fluent.Include.JqueryPulse got set
console.log( Fluent.Include.JqueryPulse );
However, I would do it without using jQuery, even if you have jQuery available on the page. There is no need for the overhead of executing a function for each index.
//bootstrap the object for demonstration purposes--not necessary to make code work
window.Fluent = {
Include: {
foo: 'bar', //don't want to lose this'
JqueryPulse: false //want to set this to true
}
};
//define function
function setGlobalItemByName( name, value )
{
var names,
finalName,
indexCount,
currentIndex,
currentName,
//no need to figure out if this should be assigned in the loop--assign it now
currentOp = window;
if( typeof name === 'string' && name !== '' )
{
names = name.split( '.' );
//no need to track where we are in the looping--just pull the last off and use it after
finalName = names.pop();
indexCount = names.length;
for( currentIndex = 0; currentIndex < indexCount; currentIndex += 1 )
{
currentName = names[currentIndex];
//If the current item is not an object, make it so. If it is, just leave it alone and use it
if( typeof currentOp[currentName] !== 'object' || currentOp[currentName] === null )
{
currentOp[currentName] = {};
}
//move the reference for the next iteration
currentOp = currentOp[currentName];
}
//object chain build complete, assign final value
currentOp[finalName] = value;
}
}
//use function
setGlobalItemByName( 'Fluent.Include.JqueryPulse', true );
//Check that Fluent.Include.foo did not get lost
console.log( Fluent.Include.foo );
//Check that Fluent.Include.JqueryPulse got set
console.log( Fluent.Include.JqueryPulse );