如何为数组中的第一个元素返回属性值，如果没有元素则返回0？

Question

In my HTML I have this code block:

<div ng-click="wos.wordWordFormRowClicked(wf)"
         ng-repeat="wf in word.wordForms">
   ...
</div>

The word object can have 0 or many wordForms and each wordForm has a property wordFormIdentityId .

In javascript how can I get the wordFormIdentityId of the first wordForm or return 0 if there are no wordForms. Hope this makes sense, if not please ask and I will try to explain more.

Here are the typescript interfaces:

interface IWord {
    wordForms: IWordForm[];
    wordId: string;
}

interface IWordForm {
    definition: string;
    wordFormId: string;
    wordFormIdentity: number;
    wordId: string;
}

Answer 1

Am I missing something or does this handle it? I responded in Typescript as well.

function getFirstId (word:IWord) :number {
    if(word && word.wordForms && word.wordForms.length > 0) {
        return word.wordForms[0].wordFormIdentity;
    }
    return 0;
}

Answer 2

I think that's what you need in your function:

if(word.wordForms)
   return word.wordForms[0].wordFormIdentity || 0;