# 8 Console Methods every JavaScript Developer should know

If you are a JavaScript developer, I am sure you have used the `console.log()` method. But, there are some other methods as well provided by the console that can make your life easier. Let's discuss some of them one by one.

# console.log()
The `console.log` method is used to print a string, number, boolean, object, or any type of data to the console. See the following example:
```
const person = {
    "id": "123",
    "name": "Bob",
    "age": 25
};
console.log(person); // prints { id: '123', name: 'Bob', age: 25 }
```
This method supports **string substitutions** and **styling**, which we will discuss at the end of this article.

# console.assert()
The `console.assert` method is used to check for the validation of data. And if the validation fails, it prints the specified error message to the console. This method also supports string substitutions and styling.

Consider the following example:
```
const person = {
    "id": "123",
    "name": "Bob",
    "age": 25
};
console.assert(person.age > 20, "You are not old enough");
console.assert(person.name.length > 4, "%s is short name", person.name);
```

![Screenshot 2022-02-12 120515.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646460999073/0Uy4O_txJ.png)

# console.count()
This method logs the number of times this line has been called with the given label. This is useful if you want to check the number of times a particular function is called with the given parameter. Let's take the example of the [Fibonacci](https://en.wikipedia.org/wiki/Fibonacci_number) function.
```
function fib (n) {
    if (n == 0) return 0;
    if (n == 1) return 1;
    return fib(n - 1) + fib(n - 2);
}
```
Now, we want to know how many times the `fib` function is called for different values of `n` when we want to calculate `fib(N)`. We can call `console.count` method and can modify the function as shown below:
```
function fib (n) {
    console.count("fib(" + n + ")");
    if (n == 0) return 0;
    if (n == 1) return 1;
    return fib(n - 1) + fib(n - 2);
}
```
Let's call the function `fib` with `n = 3` and see the output.

![Screenshot 2022-02-12 143206.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646461493898/Pg93IVo4q.png)
As we can see the final value of label `fib(1)` is `2`. It means `fib(1)` is called twice when we want to compute `fib(3)`. You can reset the count using `console.countReset(label)` method, where count of the `label` will become `0`.

# console.group()
This method is used to create a group with the given label. All the `console` statements will be placed under this group. To end the group use `console.groupEnd()` method. Here is an example:
```
console.group("Group 1");
console.log("Item 1 of Group 1");
console.group("Group 1.1");
console.log("Item 1 of Group 1.1");
console.log("Item 2 of Group 1.1");
console.groupEnd();
console.log("Item 2 of group 1");
console.groupEnd();
```

![Screenshot 2022-02-12 143817.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646461680149/0pPw6IJ63.png)
You can expand and collapse these groups. By default, all the groups are expanded. If you want a group to be collapsed by default, use `console.groupCollapsed()` method as shown below:
```
console.groupCollapsed("Group 1");
console.log("Item 1 of Group 1");
console.log("Item 2 of group 1");
console.groupEnd();
```

![Screenshot 2022-02-12 144142.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646461761338/H5lDOFi83.png)

# console.table()
If you want to see the array of objects in tabular form, use this method. For example:
```
const students = [
    { id: "123", name: "Bob", age: 25 },
    { id: "124", name: "John", age: 23, key1: "Value 1" }
];
console.table(students);
```

![Screenshot 2022-02-12 144513.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646461838649/A7GlXwo-Z.png)

# console.time()
This method is used to measure the time taken to execute some piece of code. `console.time(label)` starts the timer for `label` and `console.timeEnd(label)` stops the timer and displays the time taken. Let's say we want to calculate the time taken to compute the 20th Fibonacci number. We can do the following:
```
function fib (n) {
    if (n == 0) return 0;
    if (n == 1) return 1;
    return fib(n - 1) + fib(n - 2);
}
console.time("fib_20");
const fib_20 = fib(20);
console.timeEnd("fib_20");
```

![Screenshot 2022-02-12 145104.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646461960984/Zd9Zgp2Fm.png)

# console.trace()
This method prints the stack track of method calls at that point. Take a look at the following example:
```
function bar(n) {
    console.trace();
    return n + 1;
}
function foo(n) {
    return bar(n);
}
foo(10);
```

![Screenshot 2022-02-12 145434.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646462038828/4PMQrFxxJ.png)

# String Substitution
We can use the following substitution strings which will be replaced by the next set of arguments:

1. `%o` or `%O` for an object.
2. `%d` or `%i` for an integer.
3. `%f` for a floating-point value.
4. `%s` for a string.

For example:

![Screenshot 2022-02-12 150559.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646462184307/ljz3dy8Fk.png)

# Styling the output
You can use the `%c` directive to style the text in the console. The text after the `%c` directive will be formatted. We can use multiple `%c` directives as well in a single `log` statement. For example:
```
console.log("This is %cwhite text in green background", "color: white; background-color: green;");
console.log("This is %cblue text %cred text", "color: blue;", "color: red;", " normal text");
```

![Screenshot 2022-02-12 151300.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1646462260619/6nFtJwoXZ.png)

# Summary
There are more methods related to `console` available. You can see a list of all the methods [here](https://developer.mozilla.org/en-US/docs/Web/API/console).

Thank you 🙏 for the time to read this article. If you have any feedback, suggestions or if you want to point out any errors, feel free to comment below. Keep learning 📚...