define()

Declare your strategy parameters. Called once when the strategy loads.

Signature

function define(ctx)

Parameters

Name	Type	Description
`ctx`	`DefineContext`	Context for parameter declaration

ctx.param()

Use ctx.param() to declare each parameter:

ctx.param(name, options)

Parameter Options

Option	Type	Required	Description
`type`	`string`	Yes	`'int'`, `'float'`, `'string'`, `'boolean'`
`label`	`string`	No	Display label in UI
`description`	`string`	No	Tooltip text
`default`	`any`	Yes	Default value
`min`	`number`	No	Minimum (int/float)
`max`	`number`	No	Maximum (int/float)
`step`	`number`	No	Step size for sliders/optimization
`optimize`	`boolean`	No	Include in optimization runs
`group`	`string`	No	UI grouping
`options`	`array`	No	For string type: enum values

Example

function define(ctx) {
  ctx.param('fastLength', {
    type: 'int',
    label: 'Fast EMA',
    description: 'Period for the fast EMA',
    default: 9,
    min: 5,
    max: 50,
    step: 1,
    optimize: true,
    group: 'Trend'
  });
  
  ctx.param('slowLength', {
    type: 'int',
    label: 'Slow EMA',
    default: 21,
    min: 10,
    max: 200,
    optimize: true,
    group: 'Trend'
  });
  
  ctx.param('riskPercent', {
    type: 'float',
    label: 'Risk %',
    default: 0.02,
    min: 0.01,
    max: 0.10,
    step: 0.01,
    group: 'Risk'
  });
  
  ctx.param('direction', {
    type: 'string',
    label: 'Trade Direction',
    default: 'long',
    options: ['long', 'short', 'both']
  });
}

Parameter Types

int

Integer numbers. Use for periods, counts, lookbacks.

ctx.param('period', { type: 'int', default: 14, min: 2, max: 100 });

float

Decimal numbers. Use for percentages, multipliers.

ctx.param('threshold', { type: 'float', default: 0.5, min: 0.1, max: 1.0, step: 0.1 });

string

Text or enum values.

ctx.param('mode', { 
  type: 'string', 
  default: 'aggressive',
  options: ['conservative', 'moderate', 'aggressive']
});

boolean

True/false toggles.

ctx.param('useFilter', { type: 'boolean', default: true, label: 'Use Trend Filter' });

Accessing Parameters

Parameters are available in init() and onBar() via ctx.p:

function init(ctx) {
  ctx.indicator('ema', 'EMA', { period: ctx.p.fastLength });
}

function onBar(ctx, i) {
  if (ctx.p.useFilter && ctx.ind.ema[i] > ctx.series.close[i]) {
    return; // Skip if filter is active and price below EMA
  }
}

init() — Indicator declaration
onBar() — Trading logic
Strategy Lifecycle — Execution order