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Multiple ways to iterate dictionary in typescript |Dictionary loop Example


Typescript  Dictionary

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, contains key and value values. It is the same as map type in typescript.

Dictionary object declare in may ways, Check about declare dictionary in typescript

Let’s create an 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

for-in loop

Typescript have multiple loop syntax to iterate enumerable objects.

One way use for in loop for retrieving key and value 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 above with key and value in for of loop syntax.

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

foreach loop

  • using ES6 object have keys method introduced in ES6 version.

configure lib in tsconfig.json Tt 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 value for the given key. Finally, Print it to console.

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

});
  • In ES7 Version Another way use the ES7 version

object have entries() method introduced in 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 forEach syntax, to iterate the keys and values. Finally, Print it to 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.

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