Set Date to Today's Date (Date Only)

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "div",
  "children": [
    {
      "elmType": "span",
      "txtContent": "[$DateTripCompleted.displayValue]",
      "attributes": {
        "class": "ms-fontColor-themePrimary ms-fontColor-themeDarker--hover"
      },
      "style": {
        "display": "=if(Number([$DateTripCompleted]) ==0,'none','flex')"
      }
    },
    {
      "elmType": "button",
      "customRowAction": {
        "action": "setValue",
        "actionInput": {
          "DateTripCompleted": "=getYear(@now)+'-'+padStart(toString(getMonth(@now)+1),2,'0')+'-'+padStart(toString(getDate(@now)),2,'0')"
        }
      },
      "attributes": {
        "class": "ms-fontColor-themePrimary ms-fontColor-themeDarker--hover"
      },
      "style": {
        "border": "none",
        "background-color": "transparent",
        "cursor": "pointer",
        "display": "=if(Number([$DateTripCompleted]) ==0,'flex','none')",
        "align-items": "center"
      },
      "children": [
        {
          "elmType": "span",
          "attributes": {
            "iconName": "EventAccepted"
          },
          "style": {
            "padding-right": "6px"
          }
        },
        {
          "elmType": "span",
          "txtContent": "Mark Trip as Complete"
        }
      ]
    }
  ]
}