How to use CSS Selector in Javascript executor

 How to use CSS Selector in Javascript executor:

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querySelector()  & QuerySelectorAll UsingJSE : --> learn 

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In querySelector()  & QuerySelectorAll, we have to pass CSSSelector  and identifies element

querySelector("CSS Selector")  =  findElement(By.cssSelector(""))

querySelectorAll("CSS Selector")  =   findElements(By.cssSelector(""))

// Enter 'Sita' in first name textbox  using Css and JSE 

JS CODE : document.querySelector("input[name='firstname']").value = 'Raju';

'Raju'

//HW  get all textboxes count using CSSSelector using JSE

// querySelectorAll()  -  we pass CSS selector only and identifies multiple elements or list of webelements from page

js CODE: -->  document.querySelectorAll("input[type='text']").length;

// HW get first text box and enter some data  using querySelector()

//HW  get 2nd text box and enter some data using querySelectorAll()

Note:  

 we cannot write x'path in JavaScript code..But We can write CssSelecors in Javascript code in querySelector() , querySelectorAll() 

querySelector("CSS Selector") 

querySelectorAll("CSS Selector")