my idea is to create a separate model.js to handle these data preprocessing uniformly.

method 1: class

// model.js
class Person{
  constructor(props){
    // data   Question1:  Object.create(props)?
    Object.keys(props).forEach(prop => {
      this[prop] = props[prop];
    });
    // /
    this.name = props.firstName + props.lastName;
    this.birthDate = new Date(props.birth);
    // 0 1
    this.sex = props.sex === 0 ? "" : ""
  }
  // 
  // id
  getPhone(){
    fetch(xxx, { id: this.id }).then(...)
  }
}

// /formatlist
export const formatList = list => list.map(item => new Person(item));

method 2: agent

// model.js
const personHandler = {
  get(target, property){
    switch (property) {
      case "name":
        return target.firstName + target.lastName;
      case "birthDate":
        return new Date(target.birth);
      case "sex":
        return target.sex === 0 ? "" : "";
      // 1 
      // Question 2 targettarget.getPhone = function(){...} target 
      default: return target[property];
    }
  }
};

export const formatList = list => list.map(item => new Proxy(item, personHandler));

conclusion

for reason 1: we extract the preprocessing of this data (independent of the business logic) from the business component / logic to make the business component / logic handle the business more purely.
for reason 2: if the back-end classmate says to change id to userId, I just need to add a line of code in class or proxy to
method 1: this.id = props.userId , method 2: case "id": return target.userId

question : which of the question1 and 2.
question3: methods 1 or 2 in the comments is more suitable for this scenario. Ask the bosses for help in comparative analysis.

Review
when dealing with such scenarios in business requirements, a corresponding formatXXXData (XXX) {/ / function that processes XXX map and then return the value} is added to tools.js . This doesn"t feel very intuitive, so I"m considering whether a model.js file should be added to handle these data formatting and some business logic (such as getPhone () ) in a form similar to class Person above.
but will this increase memory overhead? After all, you need to instantiate all the dataList returned by the backend, setting a lot of properties and methods.