JSFiddle - React, Tailwind, and code Playground

JavaScript

var docs = [
 { "description": "this is string 1" },
 { "description": "this is a long string" },
 { "description": "this is a long string" },
 { "description": "this is a long string" },
 { "description": "this is a long string" },
 { "description": "this is a long string" }
];

docs.map(function(currentValue, index, array){
  currentValue['description'] = currentValue.description.slice(0,currentValue.description.length);
  return array;
});

// console.log( docs );

console.log( docs[0].description + "long string" );