Typescript:error TS2314: Generic type 'Array<T>' requires 1 type argument(s)

Question

I am learning typescript and i have written very basic code.

class School {
    nameOfStudents: Array[string];
    noOfteachers: number
    constructor(name: Array[string], no: number) {
        this.nameOfStudents = name;
        this.noOfteachers = no;
    }
    printName():void{
        for(let i=0;i<this.nameOfStudents.length;i++){
            console.log(this.nameOfStudents[i])
        }
    }
}
let arr=["a","b","c","d","e"]
let school = new School(arr,100);
school.printName();

Where ever i have used the array i am getting the following error:

error TS2314: Generic type 'Array' requires 1 type argument(s) Where i am doing wrong ?

Solution 1

Generic arrays must be defined as:

• const arr = new Array<string>()
• const arr = string[]

Solution 2

Using the T[] sythax is recommended over Array< T > synthax

TSlint rule "array-type": [true, "array"]:

For your code, Array[string] should be Array < string > in order to compile.

nameOfStudents: Array<string>;
noOfteachers: number
constructor(name: Array<string>, no: number) {
    this.nameOfStudents = name;
    this.noOfteachers = no;
}

The best practice would be something like this

class School {
    nameOfStudents: string[];
    noOfteachers: number;
    constructor(name: string[], no: number) {
        this.nameOfStudents = name;
        this.noOfteachers = no;
    }
    printName(): void {
        for (const studentName of this.nameOfStudents) {
            console.log(studentName);
    }
}

I higly recommend you to install tslint for your project, it will help you to write clean Typescript code.