update the value in json file using javascript

{ 
  "par1" : "val1",
  "par2" : "val2",
  "par3" :  { 
    "val_1" : 0, 
    "val_2" : 5
  }
}

I have a Json file, Now I want to change the value of "val_1" from '0'to '1', then how can I do this in JavaScript?

from update the value in json file using javascript