How to use the isPlaceholder function from @babel/types

Find comprehensive JavaScript @babel/types.isPlaceholder code examples handpicked from public code repositorys.

@babel/types.isPlaceholder is a function provided by the Babel Types library that checks if a given node is a "placeholder" value used in partial evaluation.

parse.js

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} else if (t.isNewExpression(parent) && key === "arguments" || t.isCallExpression(parent) && key === "arguments" || t.isFunction(parent) && key === "params") {
  type = "param";
} else if (t.isExpressionStatement(parent) && !t.isPlaceholder(node)) {
  type = "statement";
  ancestors = ancestors.slice(0, -1);
} else if (t.isStatement(node) && t.isPlaceholder(node)) {
  type = "statement";
} else {
  type = "other";
}

+ 53 other calls in file

How does @babel/types.isPlaceholder work?

@babel/types.isPlaceholder is a function provided by the Babel Types library that can be used to check if a given node is a "placeholder" value used in partial evaluation.

When called, @babel/types.isPlaceholder takes a single argument, which is the Babel node to check. The function then checks whether the node is a "placeholder" value by examining its properties and metadata.

A "placeholder" value is a special type of value used in partial evaluation, which is a technique used to evaluate only part of an expression at a time. Placeholder values are created by Babel when it encounters an expression that cannot be fully evaluated at compile-time, and are used to represent the portion of the expression that cannot be evaluated.

Here is an example of using @babel/types.isPlaceholder to check if a node is a "placeholder" value:

javascript
const t = require('@babel/types');

const node = t.identifier('foo');

console.log(t.isPlaceholder(node)); // false
console.log(t.isPlaceholder(t.numericLiteral(42))); // true

In this example, we use the @babel/types.isPlaceholder method to check if a node is a "placeholder" value. We first create an identifier node using the t.identifier method, which we know is not a "placeholder" value. We then call @babel/types.isPlaceholder on this node and log the result, which is false. We then create a numeric literal node using the t.numericLiteral method, which we know is a "placeholder" value. We call @babel/types.isPlaceholder on this node and log the result, which is true.

By using @babel/types.isPlaceholder and other methods provided by the Babel Types library, developers can manipulate and transform the abstract syntax tree (AST) of JavaScript programs, making it a valuable tool for many code analysis and optimization tasks.

Ai Example

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const t = require("@babel/types");

const node = t.identifier("foo");

console.log(t.isPlaceholder(node)); // false
console.log(t.isPlaceholder(t.numericLiteral(42))); // true

In this example, we use the @babel/types.isPlaceholder method to check if a node is a "placeholder" value. We first create an identifier node using the t.identifier method, which we know is not a "placeholder" value. We then call @babel/types.isPlaceholder on this node and log the result, which is false. We then create a numeric literal node using the t.numericLiteral method, which we know is a "placeholder" value. We call @babel/types.isPlaceholder on this node and log the result, which is true. By using @babel/types.isPlaceholder and other methods provided by the Babel Types library, developers can manipulate and transform the abstract syntax tree (AST) of JavaScript programs, making it a valuable tool for many code analysis and optimization tasks.

Other functions in @babel/types

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@babel/types.identifier is the most popular function in @babel/types (20936 examples)

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