Consolidate the foundation:
https://www.w3schools.cn/js/exercise_js.asp?filename=exercise_js_string_methods1
[String]
1. Find the position of the character h in the string txt.
var txt = "abcdefghijklm"; var pos = txt.
indexOf("h");
2. Use the slice method to return the word "bananas".
var txt = "I can eat bananas all day"; var x = txt.slice(10, 17);
3. Use the correct string method to replace the word "Hello" with the word "Welcome".
var txt = "Hello World"; txt = txt.replace("Hello", "Welcome");
4. Convert the value of txt to uppercase.
var txt = "Hello World"; txt = txt.toUpperCase();
5. Convert the txt value to lowercase.
var txt = "Hello World"; txt = txt.
var cars = ["Volvo", "Jeep", "Mercedes"]; cars[0]= "Ford";
2. Use the correct Array property to remind you of the number of items in the array.
var cars = ["Volvo", "Jeep", "Mercedes"]; alert(cars.length);
3. Use the correct Array method to delete the last item of the fruits array.
var fruits = ["Banana", "Orange", "Apple"]; fruits.pop();
4. Use the correct Array method to add "Kiwi" to the fruits array.
var fruits = ["Banana", "Orange", "Apple"]; fruits.push("Kiwi");
5. Use the splice() method to delete "Orange" and "Apple" from fruits.
var fruits = ["Banana", "Orange", "Apple", "Kiwi"]; fruits.splice( 1,2 );
6. Use the correct Array method to sort the fruits array in alphabetical order.
var fruits = ["Banana", "Orange", "Apple", "Kiwi"]; fruits.sort(); [
Date]
1. Create a Date object and remind you of the current date and time.
var d = new Date(); alert(d);
2. Use the correct Date method to extract the year (four digits) from the date object.
var d = new Date(); year = d.getFullYear();
3. Use the correct Date method to get the month (0-11) from the date object.
var d = new Date(); month = d.getMonth();
4. Use the correct Date method to set the year of the date object to 2020.
var d = new Date(); d.setFullYear(2020);
【Math】
1. Use correct mathematical methods to create a random number.
var r = Math.random();
2. Use correct mathematical methods to return the largest number between 10 and 20.
var x = Math.max(10, 20);
3. Use correct mathematical methods to round numbers to the nearest whole number.
var x = Math.round(5.3);
4. Use correct mathematical methods to find the square root of 9.
var x = Math.sqrt(9);
[Comparison operator]
1. When x is greater than y.
x = 10; y = 5; alert(x > y);
2. When x is equal to y.
x = 10; y = 10; alert(x == y);
3. When x is not equal to y, choose the correct comparison operator to alert true.
x = 10; y = 5; alert(x != y);
4. Select the correct conditional (ternary) operator. If the age is less than 18 years old, it will prompt "Too young", otherwise it will prompt "Old enough".
var age = n; var voteable = (age < 18) ? "Too young" : "Old enough"; alert(voteable);
[js conditional statement]
1. Fix the if statement to prompt "Hello World" when x is greater than y.
if (x > y){alert("Hello World"); }
2. Fix the if statement. If x is greater than y, it will prompt "Hello World", otherwise it will prompt "Goodbye".
if(x >y) { alert("Hello World"); } else{ alert("Goodbye"); }
[Switch]
1. Create a switch statement. If fruits is "banana", "Hello" will be prompted. If fruits is "apple", "Welcome" will be prompted. .
switch(fruits) { case "Banana": alert("Hello") break; case "Apple": alert("Welcome") break; } 2.
If fruits is neither "banana" nor "apple", add a The reminder ("Neither") part.
switch(fruits) { case "Banana": alert("Hello") break; case "Apple": alert("Welcome") break; default:
【for loop】
1. Create a loop from 0 to 9.
var i; for(i= 0;i< 10; i++) { console.log(i); }
2. Create a loop that iterates through each item in the fruits array.
var fruits = ["Apple", "Banana", "Orange"]; for (x of fruits) { console.log(x); }
[while loop]
1. Create a loop that runs as long as i is less than 10.
var i = 0; while(i <10) { console.log(i); i++ }
2. Create a loop that runs as long as i is less than 10, but increases i by 2 each time.
var i = 0; while (i < 10) { console.log(i); i= i+2; }
[Break loop]
1. Stop looping when i is 5.
for (i = 0; i < 10; i++) { console.log(i); if (i == 5) { break; } }
2. When i is 5, make the loop jump to the next iteration.
for (i = 0; i < 10; i++) { if (i == 5) { continue; } console.log(i); }