Multiple ways to iterate dictionary in typescript |Dictionary loop Example

Typescript dictionary class: Learn with examples.

In this Blog Post, Learn How to iterate a dictionary in typescript with examples.

Dictionary is a type of data structure with unordered list data, that contains key and value values. It is the same as map type in typescript.

Dictionary objects declare in many ways, Check about declare dictionary in typescript

Let’s create a Dictionary type interface in typescript

interface Dictionary<T> {
    [Key: string]: T;
}

Initialize the Dictionary object with data

let emps: Dictionary<string> = {};
emps["name"] = "john";
emps["id"] = "1";
emps["salary"] = "5000";

Let’s see multiple ways to iterate the dictionary object

How to iterate dictionary in typescript for-in loop

Typescript have multiple loop syntax to iterate enumerable objects.

One way is to use for in loop for retrieving keys and values from a dictionary.

for (let key in emps) {
  let value = emps[key];
  console.log(key + " : " + value);
}

Output:

"name : john" 
"id : 1" 
"salary : 5000"

for-of loop

Another way, use the for-of loop for retrieving keys and values from a dictionary.

for (const key of Object.keys(emps)) {
  let value = emps[key];
  console.log(key + " : " + value);
}

Similarly, you rewrite the above with key and value in for of loop syntax.

for (let [key, value] of Object.entries(emps)) {
  console.log(key + " : " + value);
}

Iterate typescript Dictionary using foreach loop

• using ES6 an object has the keys method introduced in the ES6 version.

configure lib in tsconfig.json to make this works in typescript.

"lib": [
    "es2016",
    "dom"
]

Object. keys returns the array of keys from a dictionary. use forEach syntax. to iterate the keys and retrieve the value for the given key. Finally, Print it to the console.

Object.keys(emps).forEach((key) => {
  let value = emps[key];
  console.log(key + " : " + value);
});

• In ES7 Version Another way to use the ES7 version

the object has theentries() method introduced in the ES2017 version. configure lib in tsconfig.json to make this works in typescript

"lib": [
    "es2017",
    "dom"
]

Object. entries returns the array of key and value pairs from a dictionary. use the forEach syntax, to iterate the keys and values. Finally, Print it to the console.

Object.entries(emps).forEach(([key, value]) =>
  console.log(key + " : " + value)
);

Conclusion

Learned typescript dictionaries loop examples to get key and value objects in multiple ways.