Hi I am trying to get a substring from a string based on some calculations but getting this error in browser console:

        
        TypeError: Cannot read properties of undefined (reading 'substring')
           at MessageVariantCardInputComponent.onInput 
           at MessageVariantCardInputComponent_input_HostBindingHandler
        

when using below code sample to get the substring value of "value"

Code:

        
      
    @HostListener('input') onInput() {  
    this.triggerFound = false;
    this.triggerName = '';
    const native = this.element.nativeElement;
    console.log("=== native dropdown", native)
    const value = native.value;
    const currentPos = native.selectionStart - 1;
    
    for (const key of Object.keys(this.triggers)) {
        const trigger = this.triggers[key];
        const triggerLen = trigger.length;
        const extractedString = value.substr(currentPos - triggerLen + 1, triggerLen);
        const found = extractedString === trigger;
        const isFirstTrigger = key === 'firstElement';
    
        if ((isFirstTrigger && found && currentPos === 0) || // allow first element trigger only when current pos is 0
            (!isFirstTrigger && found)
          ) {
                this.triggerFound = true;
                this.triggerName = trigger;
                break;
            }
        }
    }