Looping in TypeScript can often result in the error message "equals expected."

Struggling with writing a simple for loop in TypeScript:

   j: any;
  x = [1, 2, 3, 4, 5, 6, 7];
  for(j in x){
     console.log(x[j]);
  }

Encountering numerous errors even when utilizing the 'this' keyword: 1. '=' expected. 2. Cannot find name 'j'. 3. Module parse failed: You may need an appropriate loader to handle this file type.

| this.x = [1, 2, 3, 4, 5, 6, 7]; | } |
PlanningComponent.prototype.for = function (let) { | if (let === void 0) { let = j in this.x; } | console.log(this.x[j]);

4. Duplicate identifier j. 5. Unexpected token.

Seeking guidance on correcting my mistakes.

Answer №1

It is essential to include

const 

when declaring variables x and j:

const x = [1, 2, 3, 4, 5, 6, 7];
for (const j of x) {
  console.log(j);
}

Answer №2

j is unnecessary on the first line of your code, you can remove it.

Next, remember to include the const keyword for both x and in the condition of the for loop, for `j, like so:

const x = [1, 2, 3, 4, 5, 6, 7];
for(const j in x) {
   console.log(x[j]);
}

Remember: using for(var j in x) will also work. Check out more information in TypeScript for-in statement. Just make sure to use var, otherwise a global variable named j will be declared.

Answer №3

// Declaration of an undeclared variable
j: any;

// Declaration of an undeclared variable
x = [1, 2, 3, 4, 5, 6, 7];

for (j in x) {
 console.log(x[j]);
}

/*** The correct version should be ***/

let j: number = 0;
const x: number[] = [1, 2, 3, 4, 5, 6, 7];

for (; j < x.length; i++) {
  const num: number = x[j];
  console.log({index: j, value: num});
}

for...in should not be used for iterating over arrays.

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