CODEWITHSUNDEEP
javascript
HackleSaw
HackleSaw

Reputation: 139

Loop over dictionary

Js newbie here. I have two variables, the value of which I'm extracting from user input (which is a string).

Now I have a dictionary :

let dict = {
          'p':  "100 units" ,
          'q': "200  units",
          'g': "500  units",
          'e': "10  units"
        }

What I want to do here is to write a condition that allows users to enter only the key values in the dict (for example, "p for 100 units"), that is, sends a fallback response "This option is not available"(console.log) If I do this using a loop on Object.keys(dict), the response gets sent 4 times (equal to the number of key-value pairs in the dictionary).

How do I check that what the user has entered corresponds to my dictionary and send a response only once if he hasn't? I reckon I would have to loop over the dictionary in any case.

I also want to place a return for the if block. i.e:

if(whatever){
//code

return 0
}
else return 1

Any other ideas/approaches I can try?

Upvotes: 0

Views: 96

Answers (3)

FZs
FZs

Reputation: 18619

You can use the in operator to check if a key is present in an object, like:

if(input in dict){}

Using it, you can simply create a such program, where dict is your object and input is the key the user pressed:

console.log(input in dict ? 'Chosen' + dict[input] : 'Fallback text')

Upvotes: 2

iAmOren
iAmOren

Reputation: 2804

Here's some code you might find useful:

letter="e";
console.log((units=dict[letter])?letter+" for "+units:"This option is not available");

letter is the user's input. You could/should check for no input|more than one letter.
dict[letter] returns value for key letter. If not found, it returns undefined which is like false.
We assign that value to a variable units so we don't have to look it up again (useful in very complicated objects and functions to save resources).
The condition?ifTrue:ifFalse is evaluated (I've put the condition in parentheses - to avoid having to think what might be evaluated without them. Probably the same. Usually, I used this format: ((condition)?(do/value if true):(do/value if false)).
The rest should be obvious.

I would recommend consistent indentation and spacing:

let dict = {
  'p': "100 units",
  'q': "200 units",
  'g': "500 units",
  'e':  "10 units"
};
const keys = Object.keys(dict);
console.log(keys) // output ['p', 'q', 'g', 'e']

Upvotes: 1

humanshado
humanshado

Reputation: 188

Object.keys returns an array of keys like so:

let dict = {
          'p':  "100 units" ,
          'q': "200  units",
          'g': "500  units",
          'e': "10  units"}
          
  const keys = Object.keys(dict)
  console.log(keys) // output ['p', 'q', 'g', 'e']

Therefore if you want to check the letter a user enters you need to loop through the array of keys and use if statement inside the loop to check the user input:

let userInput = 'g'

for(key of keys){
  if(key === userInput){
    console.log(dict[key]) //output 500 units
  }else{
    console.log('Fall back response')
  }
}

Read the documentation here for details https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of

Upvotes: 2

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