v-model modifiers (lazy, number, trim) in Vue - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the lazy modifier do when used with v-model in Vue?

The lazy modifier updates the bound data only when the input loses focus (on change event), instead of on every input event. This can improve performance for large forms.

beginner

How does the number modifier affect the value bound by v-model?

The number modifier automatically converts the input value to a number type before updating the bound data. If the input can't be converted, the model is updated with NaN.

beginner

What is the purpose of the trim modifier in v-model?

The trim modifier removes whitespace from both ends of the input string before updating the bound data. This helps avoid accidental spaces in user input.

intermediate

How would you write a Vue input element that updates its model only after losing focus and trims whitespace?

You can use <input v-model.lazy.trim="value" />. This updates the model on change (blur) and trims spaces from the input.

intermediate

Can you combine multiple modifiers with v-model? Give an example.

Yes, you can combine modifiers like v-model.lazy.number.trim. For example: <input v-model.lazy.number.trim="age" /> updates on blur, trims spaces, and converts the value to a number.

What event triggers the model update when using v-model.lazy?

A When the input loses focus (change event)

B On every keystroke (input event)

C When the form is submitted

D When the component mounts

The lazy modifier updates the model only on the change event, which happens when the input loses focus.

What does v-model.number do to the input value?

A Converts the value to a number before updating

B Converts the value to a string

C Trims whitespace from the value

D Delays the update until form submission

The number modifier converts the input value to a number type before updating the model.

Which modifier removes spaces from the start and end of the input value?

A number

B trim

C lazy

D debounce

The trim modifier removes whitespace from both ends of the input string.

How would you write a v-model that updates on blur and converts input to a number?

A <code>v-model.number.trim</code>

B <code>v-model.trim.number</code>

C <code>v-model.lazy.trim</code>

D <code>v-model.lazy.number</code>

Combining lazy and number modifiers updates on blur and converts the value to a number.

Can you combine lazy, number, and trim modifiers together?

A No, only one modifier is allowed

B Yes, but only two modifiers at a time

C Yes, like <code>v-model.lazy.number.trim</code>

D No, they conflict with each other

Vue allows combining multiple modifiers, such as v-model.lazy.number.trim.

Explain how the lazy, number, and trim modifiers change the behavior of v-model in Vue.

Think about when the model updates and how the input value is transformed.

Describe a real-life scenario where using v-model.lazy.trim would be helpful.

Consider a form with many inputs or slow processing.