for each object array, how to add a field into it?

What I want is to insert a field index into my array

My code thar I receive my arrays is like that:

  const onFinish = (values) => {
      console.log(values.fields);

     addFields({ formName: 'TABLE NAME', fields: values.fields }).then(() => {
       //API CALL WHICH RETURNS A RESPONSE
     });
   };

values.fields is the array that I want to make it work

values.field array :

[
    {
        "field": "Peso do bezerro (kg)",
        "fieldtype": "Numeric"
    },
    {
        "field": "test",
        "fieldtype": "Text"
    },
    {
        "field": "Obs",
        "fieldtype": "Text"
    }
]

This array can have ‘x’ objects,What I want is for each add a field named index(which will get if it's the first and add 0 if the second will add a 1 and following...).Someone knows how to make it work ?

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