Unable to assign a value to an undefined property in TypeScript

I need to store data in an object and then add it to another object

let globalSamples = {} as any;
let sample = { } as ISamplesDetail [];
sample = [];
for (let i = 0 ; i<this.prelevementLingette.samplesDetail.length; i++)
    {
      sample [i].id= this.old.samplesDetail[i].id;
      sample [i].reference=this.old.samplesDetail[i].reference;
}
globalSamples.push(sample);

I encountered the error message 

'Cannot set property 'reference' of undefined'

What steps should I take to fix this issue?

typescript

Answer №1

Your code has some issues that I've addressed and cleaned up for you.

// Defining the globalSamples array with proper type
const globalSamples: ISamplesDetail[][] = [];

// Declaring a constant sample array to avoid reassignment 
const sample: ISamplesDetail[] = [];

// loop through 'this.prelevementLingette' rather than 'this.old'
for (let i = 0; i < this.prelevementLingette.samplesDetail.length; i++) {
      sample[i] = {
          id: this.old.samplesDetail[i].id,
          reference: this.old.samplesDetail[i].reference
      }
}

// Adding the sample array to the globalSamples array
globalSamples.push(sample);

It appears that there may be some logic confusion in your code, but without more context it's difficult to provide specific advice.

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