Probably \
i tried add debug configuration of NPM is inoperative,i want know why
Javascript file with this:node_modules\nuxt\bin\nuxt-dev

devtool in nuxt.config.js:extend (config, { isDev, isClient }) {
if (isDev) {
config.devtool = 'eval-source-map' // Something you like
}
}

Done!

This question has been resolved by @LancerComet, see answer.
@LancerComet in my case, this steps into a generated file pages_index.js instead of debugging inside pages/index.js itself. Is this the expected behaviour?
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Most helpful comment
Javascript filewith this:devtoolinnuxt.config.js:Done!