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A Guide to the useState Hook

A Guide to the useState Hook

Learn how to implement the useState hook.

We'll cover the following...

Implement the useState hook

Now that we have seen the data structure of useState, it's time for us to go over the source code and see how this data structure is utilized in the implementation.

The source code of useState is structured in a typical hook way in that it takes a path of either mountState or updateState, depending on if the fiber is under mount or update.

function useState(initialState) {
  // Check if the component is in the mounting phase
  if (isFiberMounting) {
    // Call the mountState function during the mounting phase
    return mountState(initialState);
  } else {
    
    // Call the updateState function during the updating phase
    return updateState(initialState);
  }
}
useState function dynamically selects using conditional statements

Let's understand the code above in which we implement a conditional mechanism in a useState hook.

  • The condition is based on whether the component is in the mounting or updating phase.

    • If the component is in the mounting phase (isFiberMounting is true), calls the mountState(initialState) function. Otherwise, calls the updateState(initialState) function.

  • The actual logic for state initialization and updates is expected to be defined in the mountState and updateState functions, respectively.

Mounting a state

When a component is under mount, the ...