Using a callback • Playground • Svelte

App.svelte

Child.svelte

import Child from './Child.svelte'

let inputBoxValue = ''

</script>

<Child onChange={newValue => inputBoxValue = newValue} />

<p>Input box value is: {inputBoxValue}</p>

import 'svelte/internal/disclose-version';

import 'svelte/internal/flags/legacy';

import * as $ from 'svelte/internal/client';

import Child from './Child.svelte';

var root = $.template(`<!> <p> </p>`, 1);

export default function App($$anchor) {

let inputBoxValue = $.mutable_state('');

var fragment = root();

var node = $.first_child(fragment);

Child(node, {

onChange: (newValue) => $.set(inputBoxValue, newValue)

});

var p = $.sibling(node, 2);

var text = $.child(p);

$.reset(p);

$.template_effect(() => $.set_text(text, `Input box value is: ${$.get(inputBoxValue) ?? ''}`));

$.append($$anchor, fragment);

}

result = svelte.compile(source, {

generate: "client" "server",

dev: false });

/* Add a <style> tag to see the CSS output */

		
			
				
					 Root {
 css: null
js: []
start: 82
end: 183
type: "Root"
fragment: Fragment {...}
 type: "Fragment"
nodes: [...] (4)
  Text {...}
 type: "Text"
start: 80
end: 82
raw: "\n\n"
data: "\n\n"
 }
 Component {...}
 type: "Component"
start: 82
end: 139
name: "Child"
attributes: [...] (1)
  Attribute {...}
 type: "Attribute"
start: 89
end: 136
name: "onChange"
value: ExpressionTag {...}
 type: "ExpressionTag"
start: 98
end: 136
expression: ArrowFunctionExpression {...}
 type: "ArrowFunctionExpression"
start: 99
end: 135
loc:  {...}
 start:  {...}
 line: 6
column: 17
 }
end:  {...}
 line: 6
column: 53
 }
 }
id: null
expression: true
generator: false
async: false
params: [...] (1)
  Identifier {...}
 type: "Identifier"
start: 99
end: 107
loc:  {...}
 start:  {...}
 line: 6
column: 17
 }
end:  {...}
 line: 6
column: 25
 }
 }
name: "newValue"
 }
 ]
body: AssignmentExpression {...}
 type: "AssignmentExpression"
start: 111
end: 135
loc:  {...}
 start:  {...}
 line: 6
column: 29
 }
end:  {...}
 line: 6
column: 53
 }
 }
operator: "="
left: Identifier {...}
 type: "Identifier"
start: 111
end: 124
loc:  {...}
 start:  {...}
 line: 6
column: 29
 }
end:  {...}
 line: 6
column: 42
 }
 }
name: "inputBoxValue"
 }
right: Identifier {...}
 type: "Identifier"
start: 127
end: 135
loc:  {...}
 start:  {...}
 line: 6
column: 45
 }
end:  {...}
 line: 6
column: 53
 }
 }
name: "newValue"
 }
 }
 }
 }
 }
 ]
fragment: Fragment {...}
 type: "Fragment"
nodes: []
 }
 }
 Text {...}
 type: "Text"
start: 139
end: 141
raw: " "
data: " "
 }
 RegularElement {...}
 type: "RegularElement"
start: 141
end: 183
name: "p"
attributes: []
fragment: Fragment {...}
 type: "Fragment"
nodes: [...] (2)
  Text {...}
 type: "Text"
start: 144
end: 164
raw: "Input box value is: "
data: "Input box value is: "
 }
 ExpressionTag {...}
 type: "ExpressionTag"
start: 164
end: 179
expression: Identifier {...}
 type: "Identifier"
start: 165
end: 178
loc:  {...}
 start:  {...}
 line: 8
column: 24
 }
end:  {...}
 line: 8
column: 37
 }
 }
name: "inputBoxValue"
 }
 }
 ]
 }
 }
 ]
 }
options: null
instance: Script {...}
 type: "Script"
start: 0
end: 80
context: "default"
content: Program {...}
 type: "Program"
start: 8
end: 71
loc:  {...}
 start:  {...}
 line: 1
column: 0
 }
end:  {...}
 line: 4
column: 0
 }
 }
body: [...] (2)
  ImportDeclaration {...}
 type: "ImportDeclaration"
start: 11
end: 45
loc:  {...}
 start:  {...}
 line: 2
column: 2
 }
end:  {...}
 line: 2
column: 36
 }
 }
specifiers: [...] (1)
  ImportDefaultSpecifier {...}
 type: "ImportDefaultSpecifier"
start: 18
end: 23
loc:  {...}
 start:  {...}
 line: 2
column: 9
 }
end:  {...}
 line: 2
column: 14
 }
 }
local: Identifier {...}
 type: "Identifier"
start: 18
end: 23
loc:  {...}
 start:  {...}
 line: 2
column: 9
 }
end:  {...}
 line: 2
column: 14
 }
 }
name: "Child"
 }
 }
 ]
source: Literal {...}
 type: "Literal"
start: 29
end: 45
loc:  {...}
 start:  {...}
 line: 2
column: 20
 }
end:  {...}
 line: 2
column: 36
 }
 }
value: "./Child.svelte"
raw: "'./Child.svelte'"
 }
 }
 VariableDeclaration {...}
 type: "VariableDeclaration"
start: 48
end: 70
loc:  {...}
 start:  {...}
 line: 3
column: 2
 }
end:  {...}
 line: 3
column: 24
 }
 }
declarations: [...] (1)
  VariableDeclarator {...}
 type: "VariableDeclarator"
start: 52
end: 70
loc:  {...}
 start:  {...}
 line: 3
column: 6
 }
end:  {...}
 line: 3
column: 24
 }
 }
id: Identifier {...}
 type: "Identifier"
start: 52
end: 65
loc:  {...}
 start:  {...}
 line: 3
column: 6
 }
end:  {...}
 line: 3
column: 19
 }
 }
name: "inputBoxValue"
 }
init: Literal {...}
 type: "Literal"
start: 68
end: 70
loc:  {...}
 start:  {...}
 line: 3
column: 22
 }
end:  {...}
 line: 3
column: 24
 }
 }
value: ""
raw: "''"
 }
 }
 ]
kind: "let"
 }
 ]
sourceType: "module"
 }
attributes: []
 }
 }

The AST is not public API and may change at any point in time

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