Error while trying to code in Google Earth Engine using Javascript

Question

I got this code but when I run it gives error message

"L8" is not defined in this scope. in, line 11 in, line 30

The code I'm using is like this

var RGB_vis = {min: 0, max: 0.3, bands: ['B4', 'B3', 'B2']};
var filtered = L8
.filterDate('2019-01-01', '2019-12-31')
.filterBounds(geometry)
.sort('CLOUD_COVER', true);
var image = ee.Image(filtered.first());
Map.addLayer(image, RGB_vis,'RGB' );

// Compute the Normalized Difference Vegetation Index (NDVI).
var nir = image.select('B5');
var red = image.select('B4');
var ndvi = nir.subtract(red).divide(nir.add(red)).rename('NDVI');
// Display the result.
Map.centerObject(image, 9);
var ndviPara ={min: -1, max: 1, palette: ['blue', 'white', 'green']};
Map.addLayer(ndvi, ndviPara, 'NDVI image');

Answer 1

You first need to define the L8 variable by inserting the Landsat 8 ImageCollection:

var L8 = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')
var RGB_vis = {min: 0, max: 0.3, bands: ['B4', 'B3', 'B2']};
var filtered = L8
.filterDate('2019-01-01', '2019-12-31')
.filterBounds(geometry)
.sort('CLOUD_COVER', true);
var image = ee.Image(filtered.first());
Map.addLayer(image, RGB_vis,'RGB' );

// Compute the Normalized Difference Vegetation Index (NDVI).
var nir = image.select('B5');
var red = image.select('B4');
var ndvi = nir.subtract(red).divide(nir.add(red)).rename('NDVI');
// Display the result.
Map.centerObject(image, 9);
var ndviPara ={min: -1, max: 1, palette: ['blue', 'white', 'green']};
Map.addLayer(ndvi, ndviPara, 'NDVI image');