Null Value
beginnerDefinition
A special placeholder meaning 'no data here.' Null is different from zero, an empty string, or false. Those are all real values. Null means the value is deliberately absent or unknown. Forgetting to handle null is one of the most common sources of bugs.
In the wild
A user who never set a phone number has phone: null: not phone: '' (empty string) or phone: 0. If your code tries user.phone.length without checking for null first, it crashes with 'Cannot read property length of null.'
More from Data & Transformation
Aggregation
Combining many individual data points into a summary. Aggregations answer questions like 'how many,' 'what's the total,' or 'what's the average' by collapsing a list of values into a single result.
Data Pipeline
An automated flow that extracts data from a source, transforms it into a useful shape, and loads it into a destination. Often called ETL (Extract, Transform, Load). Data pipelines run on a schedule to keep dashboards, reports, and databases up to date.
Deduplication
Removing duplicate entries from a dataset so each record appears only once. Duplicates creep in when data is imported from multiple sources, forms are submitted twice, or syncs overlap. Deduplication keeps your data clean and your counts accurate.
Normalization
Restructuring data to reduce duplication and inconsistency. Instead of repeating the same information in multiple places, normalization splits data into related tables or structures and connects them with references.
Parsing
Reading raw text and extracting structured information from it. Parsing turns unstructured data (a string, a file, a response body) into something your code can work with: objects, arrays, numbers, dates.
Schema
A blueprint that defines the expected shape of your data: what fields exist, what types they are, and which ones are required. Schemas catch bad data early by rejecting anything that doesn't match the expected structure.