如何在Component template函数执行时查看ɵɵtemplate或者ɵɵproperty传入的参数值

在观察template执行的时候，如下图所示：展开ng-template时：

会触发函数ɵɵproperty的执行：

/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
/**
 * Update a property on a selected element.
 *
 * Operates on the element selected by index via the {@link select} instruction.
 *
 * If the property name also exists as an input property on one of the element's directives,
 * the component property will be set instead of the element property. This check must
 * be conducted at runtime so child components that add new `@Inputs` don't have to be re-compiled
 *
 * @param propName Name of property. Because it is going to DOM, this is not subject to
 *        renaming as part of minification.
 * @param value New value to write.
 * @param sanitizer An optional function used to sanitize the value.
 * @returns This function returns itself so that it may be chained
 * (e.g. `property('name', ctx.name)('title', ctx.title)`)
 *
 * @codeGenApi
 */
function ɵɵproperty(propName, value, sanitizer) {
    const lView = getLView();
    const bindingIndex = nextBindingIndex();
    if (bindingUpdated(lView, bindingIndex, value)) {
        const tView = getTView();
        const tNode = getSelectedTNode();
        elementPropertyInternal(tView, tNode, lView, propName, value, lView[RENDERER], sanitizer, false);
        ngDevMode && storePropertyBindingMetadata(tView.data, tNode, propName, bindingIndex);
    }
    return ɵɵproperty;
}

如果想查看第二行layoutName$变量的值，在debugger里查看arguments:

展开source:

source._value里的header就是layoutName$准备emit出去的值。

更多Jerry的原创文章，尽在：“汪子熙”: