How to remove string datatype in append array of multiple objects through form data in react.js

I am integrating varientform.i have recieving array of object in state.but when im trying to submit data so im getting this kind of data in console

varientDetails: [
‘{“index”:0.2731402713862625,”sort”:”45″,”sku”:”5″,”waightorquantity”:”1″,”Unit”:””,”mrp”:””,”discount”:””,”price”:””,”stock”:””,”minstock”:””,”outofstock”:””}’
]

im using this code……
varientDetails.forEach(varient =>{formData.append(varientDetails[],JSON.stringify(varient))})