How to write the value passed by the vue typescrip child component to the parent component

how to write the value passed by the vue typescrip child component to the parent component.
can"t trigger with @ emit

Mar.22,2021

component code


export default class HelloWorld{
    emitValue = {value:1} // here
    @Emit('onHelloClick')
    componentHandleClick(val: any) {
        console.log('emit step 1')
        this.emitValue.value += 1 // here
        console.log('emit step 2')
    }
}
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