Today #day22 of #100daysofcode, I have completed 2 lessons and a practice program in JS. @Sololearn

1. Function

Printing to browser

• document.write() function will write into the html document.

  document.write("Hello World!");
  document.write("<br>this will be displayed in html doc")
  console.log('this will appear in Console')
  

• use html tags to give appearance overhaul.

  document.write("<b><h1></b>Hello World!<b></h1></b>");
  document.write("<b><h1></b>Javascript rocks<b></h1></b>")
  

Note

• document.write() should be used only for testing.
• innerHTML, used to manipulate HTML elements.
• console.log(), used for debugging in browser console.

2. Variables

How to store data values?

• Variables are containers which stores data values. The value of variable changes throughout JS code.
• use keyword var to declare a variable.

  var x = 2;
  

Note:

• Here we have used assignment operator called equal to =.
• JavaScript is case sensitive language.

  var a = 8; var A = 10; alert(a); 
  /* Alert is 8 as Javascript is case sensitive */
  

• using keywords as variable name is prohibited.

Example:

var x = 100;
document.write(x);
x=2;
document.write("<br>"+x);

Note:

• Every instruction in JavaScript is a statement and statements are separated by;.

Naming Variables

• As discussed, earlier JavaScript variables are case sensitive. The following code will throw an error.

  var x = 39;
  document.write(X);
  

Do's

The first character of a variable name should be / must be

• a letter
• underscore(_)
• $

Don'ts

1. The first character of a variable name can't be
   • a number
2. Variable names can't contain
   • mathematical or logical operator. var x+next
   • spaces.
   • special symbols. var stu@

Note

• JavaScript is a hyphen free zone. They’re reserved for subtractions.

Image

Conclusion

• Printing to browser using document.write().
• storing data values using variables.
• do's and don'ts in using a variable.
• practice program.

References Sololearn

Author: Dheeraj.y

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