Parse Json in Javascript - Google Tag Manager

Question

I do have that script:

function() {
  var publishedDate = "";
  var yoastInfo = JSON.parse(document.head.querySelector('.yoast-schema-graph.yoast-schema-graph--main').innerHTML);
  vars = yoastInfo["@graph"];
  for(var i in vars) {
    if(vars[i]['@type'] === 'WebPage') {
      pubDateRaw=(vars[i]['datePublished']);
      break;
    }
  }
  publishedDate.concat(pubDateRaw.substring(0,4),pubDateRaw.substring(5,7),pubDateRaw.substring(8,10));
  return publishedDate;
}

When I run the code, it gives me a "" instead of the date.

here is the json:

{
  "@context": "https://schema.org",
  "@graph": [   

    {
      "@type": "WebPage",
      "@id": "id234234",
      "url": "https://www.whatevver.com",
      "inLanguage": "de-DE",
      "name": "this is the name",
      "isPartOf": {
        "@id": "id234234
      },
      "primaryImageOfPage": {
        "@id": "id234234"
      },
      "datePublished": "2020-01-14T07:46:12+00:00",
      "dateModified": "2020-01-15T08:04:50+00:00",
      "description": "description "
    },

  ]
}

So i need to extract the datePubished from that json. What is wrong with my code?

Edit

With the help of you guys, I made this script:

function() {
  var publishedDate = "";
  var yoastInfo = JSON.parse(document.head.querySelector('.yoast-schema-graph.yoast-schema-graph--main').innerHTML); 
  vars = yoastInfo["@graph"];
  for(var i in vars) {
    if(vars[i]['@type'] === 'WebPage') {
      publishedDate=(vars[i]['datePublished']); 
    }
  }



  return publishedDate;
}

now I need to cut the dateTime 2020-01-14T07:46:12+00:00 to 2020-01-14 what would be the best solution?

EDIT2

Found the Solution at: To the Solution

Answer 1

Given JSON :

{
  "@context": "https://schema.org",
  "@graph": [   

    {
      "@type": "WebPage",
      "@id": "id234234",
      "url": "https://www.whatevver.com",
      "inLanguage": "de-DE",
      "name": "this is the name",
      "isPartOf": {
        "@id": "id234234" // MAKE IT AS A STRING
      },
      "primaryImageOfPage": {
        "@id": "id234234"
      },
      "datePublished": "2020-01-14T07:46:12+00:00",
      "dateModified": "2020-01-15T08:04:50+00:00",
      "description": "description "
    },

  ]
}

function() {
  let publishedDate = "";
  const yoastInfo = JSON.parse(document.head.querySelector('.yoast-schema- 
  graph.yoast-schema-graph--main').innerHTML); // I HOPE YOURE ABLE TO EXTRACT THE JSON HERE IN yoastInfo.
  vars = yoastInfo["@graph"];
  for(var i in vars) {
    if(vars[i]['@type'] === 'WebPage') {
      publishedDate=(vars[i]['datePublished']); // YOU ARE GETTING EMPTY STRING BECAUSE YOU'RE SETTING VARIABLE CALLED 'publishedDate' AND SETTING VALUE IN 'pubDateRaw'.
    }
  }
  return publishedDate;
}

PLEASE FOLLOW THE COMMENTS IN THE CODE FOR CLARIFICATION. THANKS :))

And check the link for more clarification: https://jsfiddle.net/gahzsrvj/1/