Property not being added to object

I have a object which has an array inside it. Each array has multiple objects. So using the .map function I am looping over the array inside the object. Each array item has a click function where I toggle the item. Initial state of the array item is this

{    DisplayText: "Foresatte"    Selectable: true    UserRecipientToInclude: "IncludeGuardianRecipient"}

When I do this

choice.Selected = false

and console logs the result the newly added item is not present in the object. Why is that?

Here is the code

<TouchableHighlight  {...testProperties(choice.DisplayText, true)}  style={{ opacity: !choice.Selectable ? 0.4 : 1 }}  onPress={() => {    this.selectChoice(c.UserDropdownMenuChoices, choice, c)  }}  underlayColor={'transparent'}  key={choice.DisplayText}><View style={styles.choiceContainer}>    {      choice.selected ? (        //<MaterialCommunityIcons name={'checkbox-marked'} style={styles.checkboxClick} size={20} /><Icon          type={'material-community'}          name={'checkbox-marked'}          iconStyle={styles.checkboxClick}          size={20}        />      ) : (<Icon          type={'material-community'}          name={'checkbox-blank-outline'}          iconStyle={styles.checkboxDefault}          size={20}        />      )      //DONE: <MaterialCommunityIcons name={'checkbox-blank-outline'} style={styles.checkboxDefault} size={20} />    }<Text style={styles.displayText}>{choice.DisplayText}</Text></View></TouchableHighlight>

and my function is like this

  selectChoice(choicesList, choice, contact) {    choice.selected = true    ...    console.log(choice) // doesn't have the new property  }

This code is for a react native application